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Noise Levels in Hong Kong PrimarySchools: Implications for classroomlisteningChing Yee Choi a & Bradley McPherson aa University of Hong Kong , ChinaPublished online: 22 Jan 2007.

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International Journal of Disability, Development and EducationVol. 52, No. 4, December 2005, pp. 345–360

ISSN 1034-912X (print)/ISSN 1465-346X (online)/05/040345–16© 2005 Taylor & FrancisDOI: 10.1080/10349120500348714

Noise Levels in Hong Kong Primary Schools: Implications for classroom listening

Ching Yee Choi and Bradley McPherson*University of Hong Kong, ChinaTaylor and Francis LtdCIJD_A_134854.sgm10.1080/10349120500348714International Journal of Disability, Development and Education1034-912X (print)/1465-346X (online)Original Article2005Taylor & Francis524000000December 2005BradleyMcPhersonFaculty of EducationUniversity of Hong KongPokfulam RoadPokfulamHong Kongdbmcpher@hkucc.hku.hk

Many researchers have stressed that the acoustic environment is crucial to the speech perception,academic performance, attention, and participation of students in classrooms. Classrooms inhighly urbanised locations are especially vulnerable to noise, a major influence on the acousticenvironment. The purpose of this investigation was to determine noise levels in one such urbanenvironment, Hong Kong. The ambient noise level, and its relationship to the speech intensitylevels of both teachers and students was surveyed in 47 primary school classrooms. Moreover, thepresence of acoustical treatments for noise reduction and the use of classroom amplificationsystems were documented for each classroom. The survey found that the mean occupied noiselevel was 60.74 dB (A); the mean unamplified and amplified speech-to-noise ratios of teacherswere 13.53 dB and 18.45 dB, respectively; while the mean unamplified speech-to-noise ratio forstudents was 4.13 dB. Most of the classrooms exhibited insufficient acoustical treatments toprovide significant noise reduction. The listening environment in many Hong Kong primaryschools was not favourable for optimal classroom learning. Recommendations for improving theacoustical environment in classrooms in highly urbanised locations such as Hong Kong arediscussed.

Keywords: Classroom acoustics; Listening environment; Noise; Primary schools; Speech level

Introduction

Learning in classrooms is mainly facilitated through verbal and auditory communica-tion between teachers and students (Flexer & Long, 2003). Hence, accurate speechrecognition by students is a prerequisite for learning to take place. Accurate speech

*Corresponding author. Faculty of Education, University of Hong Kong, Pokfulam Road, Pokfulam,Hong Kong. Email: dbmcpher@hkucc.hku.hk

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recognition is affected by cognitive factors (e.g., students’ intellectual abilities),linguistic factors (e.g., teachers’ articulatory abilities and students’ language levels),as well as acoustic factors (e.g., classroom noise level) (Crandell & Smaldino, 1994).Acoustic factors, typically, have the most adverse impact on speech perception inclassrooms (Polich & Segovia, 1999). Hence, an optimal acoustical environment isimportant for and can benefit all children in all classrooms.

An unfavourable listening environment can adversely affect children, especiallyyounger listeners who have immature auditory and linguistic systems (Nelson &Soli, 2000). Children under the age of 15 years are the largest population at risk fornoise interference in classrooms (Crandell & Smaldino, 2000b). In addition, chil-dren with conductive hearing loss, a history of or recurrent otitis media, language orarticulation disorders, dyslexia, learning difficulties, central auditory processingdeficit, unilateral or minimal degrees of bilateral sensorineural hearing loss, develop-mental delays, or attention deficits exhibit more perceptual difficulties in typicalclassroom environments than other children (Crandell & Smaldino, 1992, 1994,1996, 2000b; Crandell, Smaldino, & Flexer, 2004; Nabelek & Nabelek, 1994).

Measures of acoustical barriers that can compromise learning in classroomsinclude the background noise level, the speech-to-noise ratio, the reverberation time,and the speaker-to-listener distance (Crandell & Smaldino, 2000b). Investigations ofthese acoustical variables in classrooms have been reported in many studies (Finitzo-Hieber & Tillman, 1978; Markides, 1986; Massie, Theodoros, Byrne, McPherson, &Smaldino, 1999; Polich & Segovia, 1999; Rosenberg et al., 1999). The backgroundnoise level and the speech-to-noise ratio have been the most studied variables. Themost deleterious factor affecting classroom acoustics is excessive noise (Berg, Blair,& Benson, 1996). Ambient noise compromises student speech perception by maskingthe acoustic cues present in the speech signals of teachers. In addition, it adverselyaffects academic achievement and the on-task behaviours of students, and may alsoaffect the performance of teachers in classrooms (Crandell et al., 2004).

In general, ambient noise in classrooms is defined as any kind of unwanted audi-tory disturbance that interferes with student willingness and ability to perceive in aclassroom (Finitzo-Hieber, 1988). Ambient noise in a classroom mainly originatesfrom three sources: external noise, internal noise, and noise that is generated withinthe classroom itself. External noise refers to any noise that is created outside theschool building. Noise from nearby traffic, construction sites, and surroundingbuildings are some sources of external noise. Schools in highly urbanised localitiesare especially vulnerable to external noise. Hong Kong, the region of focus in thisstudy, with 6,787,000 persons, is one of the 25 most populous world cities, with avery high population density—6,300 people per square kilometre (Government ofHong Kong, 2002). Internal noise is defined as noise generated within the schoolbuilding but outside the classroom. Noises originating from a music room, canteen,or gymnasium adjacent to a classroom are examples of internal noise. Any noise thathas its origin inside a classroom, such as student talk, sliding of tables and chairs,and noise from the improper functioning of air-conditioning or ventilators, isregarded as classroom noise (Crandell & Smaldino, 1994, 1996, 2000a, 2000b).

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Noise Levels in Primary Schools 347

One might presume in the light of Hong Kong’s high population density that ambi-ent classroom noise levels would be high.

Speech-to-noise ratio is regarded as the most important measure for considerationwhen gauging accurate speech perception in classrooms (Crandell & Smaldino,2000b). The ability of a listener to perceive speech in classrooms is affected by boththe intensity of the speech signal of the speaker and the intensity of the backgroundnoise of the classroom, not just by the level of absolute ambient noise (Crandell et al.,2004). The relationship between these two variables is defined as the speech-to-noiseratio of the classroom. For example, if the ambient noise level of a classroom is 60 dB(A) while the speech level of the teacher is 65 dB (A), the resulting speech-to-noiseratio is 65 dB − 60 dB, or +5 dB. The greater the speech-to-noise ratio, the morefavourable the environment is for speech perception.

Classroom acoustical guidelines for normal hearing children have not been fullydeveloped in most countries. However, numerous investigators have recommendedthat the unoccupied noise level be within a 30–40 dB (A) range, while the occupiedlevel should not exceed 50 dB (A) for optimal student learning (American Speech–Language–Hearing Association [ASHA], 2005; Berg, 1993; Crandell & Smaldino,1996; Crandell et al., 2004). Children with normal hearing need a signal-to-noiseratio of +10 to +15 dB to achieve adult-like performance in speech recognition,while a more favourable level of +15 dB is needed for at-risk children (e.g., childrenbelow the age of 15 years, children with auditory disorders) (Berg; Smaldino &Crandell, 2000). Most studies suggest that the recommended criteria for ambientnoise levels and speech-to-noise ratios in learning environments should follow themost stringent level in order to attain maximum communication for all listeners(ASHA; Crandell & Smaldino, 1996, 2000b; Crandell et al.; Nelson & Soli, 2000).Hence, the ASHA has recommended that speech-to-noise ratios should equal orexceed +15 dB while the suggested unoccupied ambient noise level should notexceed 30–35 dB (A) (ASHA, 2005). This recommendation was based on similarrecent American National Standards Institute (2002) guidelines.

Many studies have attempted to investigate the ambient noise level in classrooms,and a review of these studies indicates that acoustical recommendations are rarelyachieved (Finitzo-Hieber, 1988; Knecht, Nelson, Whitelaw, & Feth, 2002; Rosen-burg et al., 1999). For example, the average occupied classroom background noiselevel for 33 primary schools in Florida was reported to be 62.63 dB (A) and none ofthe classrooms met recommended standards (Rosenberg et al., 1999). The ambientnoise levels for 32 classrooms in eight central Ohio primary schools were found to bebetween 28 and 68 dB (A), and only two of the classrooms met the standard recom-mended by ASHA (Knecht et al., 2002).

A number of studies have also investigated the speech-to-noise ratios found inclassrooms. Rosenberg et al. (1999) reported that the mean amplified speech-to-noise ratio was 3.31 dB, while the unamplified ratio was –3.63 dB. In an earlierstudy (Finitzo-Hieber, 1988), speech-to-noise ratios were found between +2 and +4dB. Hence, less than favourable speech-to-noise ratios are usually reported in theliterature.

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There are various ways to improve a classroom listening environment. Some meth-ods, such as the relocation of schools or classrooms to a quieter place, are impracticalfor existing classrooms. However, acoustical modifications such as double-panedwindows can help in attenuating the external and internal noise sources (Crandell &Smaldino, 1994). To minimise classroom noise the rearrangement of listeners awayfrom high noise sources, such as fans, air-conditioners, or ventilators, may bepossible. The use of acoustical modifications, such as carpeting, acoustically treatedfurniture, or curtains, are an alternative means to reduce within-classroom noise.Unfortunately, effective acoustical treatments are generally reported in the literatureto be little used (Crandell & Smaldino, 1994; Rosenberg et al., 1999). For example,in the previously mentioned Florida study of 60 classrooms, 86.7% exhibited bothacoustic ceiling tiles and carpeting, but only 10% contained drapes and none of therooms had acoustically modified furniture (Rosenberg et al., 1999).

An alternative means to improve classroom speech-to-noise ratio is to use class-room amplification. Typically, this involves the use of sound-field (SF) amplificationdevices that employ a wireless microphone proximal to the teacher to transmitspeech output to an amplifier-loudspeaker system (Smaldino & Crandell, 2000).The amplified speech of the teacher (or of a student using the microphone) canprovide up to a 10 dB improvement in the speech-to-noise ratio throughout a class-room (Crandell et al., 2004). Many investigations show the benefits of using amplifi-cation for both students and teachers (Massie et al., 1999; Rosenberg et al., 1999;Sapienza, Crandell, & Curtis, 1999). At present, SF systems are uncommon inHong Kong. However, in recognition of the problems associated with high levels ofambient noise, many teachers in Hong Kong use fixed or portable public addresssystems during lessons. These systems usually comprise a large, hand-held micro-phone connected by hardwire or wireless link to an amplifier and single loudspeakerthat is placed at the front of the classroom.

Although the need for a favourable learning environment is well known, no studyhas provided a description for the actual acoustic situation in primary schools inhighly urbanised Hong Kong. Therefore, the purpose of the present study was tosurvey the acoustical environment in primary classrooms in Hong Kong. Classroomsin primary schools are targeted because, as mentioned earlier, young children in theearly grades have the greatest need for an advantageous learning environment(Rosenberg et al., 1999). In the present study, measurements of the ambient noiselevels in classrooms were taken, the relationship between classroom noise level andthe speech levels of teachers and students was established, and the presence ofacoustical treatments for noise reduction in classrooms was documented.

Method

Information concerning the aims and procedures of this study was sent to the princi-pal teachers of 30 randomly selected government primary schools throughout HongKong. Schools were invited to participate in the study, and 11 different primaryschools agreed to take part, with a participation rate of 36.7%. Forty-seven

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randomly selected classrooms located in these primary schools were evaluated. In allcases, classroom teachers and selected students gave their informed consent to havemeasurements recorded of their speech levels during a class activity. As shown inTable 1, the classrooms were located in schools with various surroundings.

The study consisted of two parts: descriptive information about the environmentand the acoustical treatments of the classrooms obtained through observations andinterviews; and noise and speech level measurements conducted on site.

Descriptive Information

Classroom environments. Information concerning the total number of students ineach class, the size of the classroom, the height of the ceiling, and the year ofconstruction of the school were recorded during site visits by the first author. Inaddition, the presence of sound field amplification or portable public addresssystems and heating, ventilation, and air-conditioning systems was documented.

Acoustical treatments. An author-developed checklist concerning the presence ofacoustical treatments in each classroom was documented. The following acousticaltreatments were recorded in each classroom: (a) carpet; (b) draperies or acousticallytreated Venetian blinds; (c) acoustic ceiling tiles; (d) partitions for forming barriersbetween teaching and other areas of the classroom; (e) acoustical wall treatments, suchas cork bulletin boards; (f) acoustically modified furniture; and (g) double-glazedwindows. Items (a) to (f) were the acoustical treatments usually reported in the liter-ature (Rosenberg et al., 1999). Item (g) was added as the use of double-glazed windowsmay be one of the most practical acoustical treatments for Hong Kong schools.

Acoustic Measurements

Both speech levels and noise levels were measured using a calibrated Brüel & KjærSLM type 2235 sound-level meter equipped with a quarter-inch condenser micro-phone type 4176 and associated octave filter set, Brüel & Kjær model 1625. All themeasuring equipment had been calibrated in accordance with the requirements asspecified in IEC 651 and IEC 804 standards. The measurements were obtainedusing the A-weighting network. This is the most widely adopted scale for classroom

Table 1. Location of the participating schools and classrooms

Location Number of schools Number of classrooms

High external noise (e.g., near to main traffic roads) 3 14Medium external noise (e.g., near to small roads or

in residential areas)6 24

Lower external noise (e.g., in urban fringe areas) 2 9Total 11 47

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measurements. The following measurements were carried out during quiet, mainlynon-verbal, class activities in each classroom by the first author.

Noise levels. Occupied classroom noise levels were measured with the dB (A) slowscale. In addition, noise levels with the dB linear (SPL) scale at 500, 1000, 2000 and4000 Hz, in third-octave bands, were obtained. Due to time constraints and limitedroom availability, measurements were taken at one location (the central point) foreach classroom. Occupied classroom noise measurements were obtained during peri-ods when classes were ongoing and teachers and students were generally not talking(e.g., completing written exercises). The noise level was obtained by making threemeasurements at 10-min intervals during a 30-min lesson and by averaging the results.

Speech levels. Both the teachers and the students were instructed to use their voiceas in a normal lesson. The unamplified and amplified speech level measurements ofteachers were taken approximately 2 m from the mouth of the teacher or from theloudspeaker (if used by a teacher) to the microphone of the sound-level meter,respectively. The 2 m distance was selected as it was an average of the variations thattypically occurred in the distance between teacher and students in a classroomsetting (Markides, 1986). The speech level was obtained when teachers were givinginstructions in a formal lesson. Three samples were recorded; at the beginning, inthe middle, and at the conclusion of a 30-min session. The speech level taken wasthe average value of these three attempts.

Regarding the speech level measurements of students, one male and one femalestudent were randomly selected from the class in order to find representative samplesfor vocal intensity. Speech levels were measured with a 2-m distance from theirmouths to the microphone. The 2-m distance also represents approximately the great-est student-to-student distance in a normal classroom setting (Markides, 1986). Themeasurements were obtained by having the students read a text passage aloud. Threesamples were taken; at the beginning, in the middle, and at the end of the passage.

Speech-to-noise ratio. The average levels obtained for speech by teachers andstudents were subtracted from the average noise level of each classroom to obtain anindication of the speech-to-noise ratios of teachers and students in each classroom.

Test–retest reliability. To gauge the test–retest reliability of the acoustic measure-ments, the same procedures were repeated in two randomly selected schools (eightclassrooms) 1 week after the completion of the first visit. Measurements taken onboth occasions were compared and the absolute differences between them wereobtained. The mean absolute difference for each measurement was compared withthe measurement error tolerance level allowed by the IEC 651 standard for Type 1sound-level meters, so as to check the relative magnitude of the measured differ-ences between visits.

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Noise Levels in Primary Schools 351

Results

Descriptive Information

Classroom environment. Forty-seven classrooms in 11 primary schools were includedand evaluated in this investigation. These classrooms were constructed between1958 and 1989. The size of the classrooms was between 47.52 and 52.50 m2 whilethe height of ceiling was between 3.10 and 3.30 m. The mean number of students ineach classroom was 34.49 (range = 23–45). Four (8.51%) classrooms used tempo-rary walls for the separation of classrooms from other classrooms. Fixed publicaddress amplification systems were installed in 18 classrooms (38.30%) and twoclassrooms (4.26%) used portable public address systems. Regarding heating, venti-lation, and air-conditioning systems, 25 classrooms (53.19%) had air-conditionersand ventilators while all classrooms had ceiling fans.

Acoustical treatments. The most commonly used acoustical treatments were corkbulletin boards. All classrooms were equipped with this item. Only four (8.51%) outof the 47 classrooms had double-glazed windows, and none of the classrooms usedacoustically modified furniture, partitions, carpet, draperies or acoustically treatedVenetian blinds, or acoustic ceiling tiles.

Acoustic Measurements

Noise levels. The mean noise level of the 47 occupied classrooms was 60.74 dB (A)(SD = 3.16 dB (A), range = 54.13–67.63 dB (A)). Individual classroom noise levelswith the dB A-weighting scale are noted in Figure 1.Figure 1. Average noise levels in 47 Hong Kong primary school classroomsAs shown in Figure 1, none of the classrooms had noise levels below 50 dB (A),one (2.13%) of the classrooms had a noise level below 55 dB (A), and the majorityof classrooms (87.23%) had noise levels between 55 and 65 dB (A), while theremaining five classrooms (10.64%) exhibited noise levels in excess of 65 dB (A).

The mean noise levels in dB SPL at 500, 1000, 2000 and 4000 Hz were 57.1,53.5, 49.7 and 45.5 dB SPL, respectively. There was a decrease in the mean noise

05

10152025303540455055606570

0 5 10 15 20 25 30 35 40 45 50

Occupied Classroom

Figure 1. Average noise levels in 47 Hong Kong primary school classrooms

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levels from low-frequency sound at 500 Hz (M = 57.13 dB SPL, SD = 3.05 dBSPL) to high-frequency sound at 4000 Hz (M = 45.54 dB SPL, SD = 2.54 dB SPL).Results from a t-test of independent samples revealed that the difference of 11.59 dBSPL between measures at these two frequencies was statistically significant [t(92) =20.02, two-tailed, p < .05].

Speech levels. The mean unamplified and amplified speech levels of teachers were73.32 dB (A) (SD = 1.88 dB (A), range = 70.27–79.90 dB (A)) and 81.94 dB (A)(SD = 4.17 dB (A), range = 75.00–87.40 dB (A)), respectively. There was a differ-ence of 8.62 dB (A) between the mean speech levels of teachers with and withoutamplification, which was significant [t(45) = 9.78, two-tailed, p < .05].

The speech levels among the individual teachers who were not using amplifica-tion devices were higher than typically expected conversational speech intensity.Among the 35 teachers, all had speech levels over 65 dB (A), while 31 (88.57%)had speech levels between 70 and 75 dB (A) and the remaining four (11.43%) hadspeech levels greater than 75 dB (A). Speech levels for the 12 teachers using ampli-fication devices were, as expected, more intense. Four (33.33%) of teachers hadmeasured amplified speech levels less than 80 dB (A), five (41.67%) between 80and 85 dB (A), and the remaining three (25.00%) had amplified speech levels inexcess of 85 dB (A).

The mean speech levels of male and female students were 65.29 dB (A) (SD =2.31 dB (A), range = 61.40–73.57 dB (A)) and 64.44 dB (A) (SD = 2.38 dB (A),range = 60.87–72.77 dB (A)) respectively. A difference of 0.85 dB (A) was notedbetween the average speech levels of the male students and that of the femalestudents and the difference was not significant [t(92) = 1.75, two-tailed, p > .05].

Among the 94 students, the mean speech level was 64.87 dB (A) (SD = 2.37 dB(A)), while the highest speech level noted was 73.57 dB (A) and the lowest was60.87 dB (A). Thirty-nine students (41.49%) gave speech levels equal to or greaterthan 65 dB (A).

Speech-to-noise ratios. The mean unamplified speech-to-noise ratio of teachers was13.53 dB (SD = 3.32 dB, range = 7.13–20.00 dB) while that of the teachers usingamplification was 18.45 dB (SD = 3.82 dB, range = 12.13–22.07 dB). A significantdifference of 4.92 dB was noted between the mean amplified and unamplified condi-tions [t(45) = 4.27, two-tailed, p < .05]. As shown in Figure 2, among the 12 ampli-fied speech-to-noise ratios of teachers, all exceeded +10 dB, while nine (75.00%)reached +15 dB or above. For the 35 unamplified speech-to-noise ratios of teachers,all were greater than +6 dB, 30 (85.71%) exceeded +10 dB, and nine (25.71%)reached +15 dB or above.Figure 2. Speech-to-noise ratio of amplified teachers, unamplified teachers, and studentsThe average speech-to-noise ratio was 4.55 dB (SD = 3.34 dB, range = −2.60 to11.57 dB) for male students and 3.71 dB (SD = 3.11dB, range = −3.80 to 8.33 dB)for female students. A t-test for independent samples revealed no significant differ-ence between the speech-to-noise ratios of both male and female students [t(92) =

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1.29, two-tailed, p > .05]. The mean speech-to-noise ratio for 94 students was 4.13dB (SD = 3.24 dB, range = –3.80 to 11.57 dB). As shown in Figure 2, negativespeech-to-noise ratios were obtained for nine (9.57%) of the male and femalestudents. Positive speech-to-noise ratios were obtained for 85 students (90.43%),while 28 (29.79%) exceeded +6 dB, three (3.19%) reached +10 dB or more, but nostudent had +15 dB or greater.

Test–retest reliability. As presented in Table 2, the absolute differences for meannoise level measurements (range = 0.69–0.89 dB) between the two visits wereapproximate to the measurement error tolerance level of 0.5 dB allowed by the IEC651 standard for Type 1 sound-level meters (International ElectrotechnicalCommission, 1979). Slightly greater absolute differences were found for the speechlevel measurements (range = 0.95–1.87 dB (A)) and speech-to-noise ratio measure-ments (range = 1.19–1.76 dB), most probably due to inherent intensity variations ofhuman speech. In summary, all the differences were within 2 dB, which was unlikelyto significantly affect the results of the present study.

Discussion

The present study aimed at investigating the ambient noise levels found in HongKong primary school classrooms and establishing the typical intensity of speech levelsfor both teachers and students. In addition, the use of acoustical treatments for noisereduction in these classrooms was documented. Results revealed that all of the class-rooms exceeded the recommended maximum noise level of 50 dB (A), with a meanambient noise level of 60.74 dB (A). The amplified and unamplified speech-to-noiseratios of teachers were 18.45 dB and 13.53 dB, respectively, and the speech-to-noiseratio of students was 4.13 dB. The unamplified teacher speech-to-noise ratio and thestudent speech-to-noise ratio also failed to meet +15 dB recommendations. In addi-tion, the use of acoustical modifications for noise reduction was found to be uncom-mon in the surveyed classrooms. The following discussion concerns the audiologicalimplications and recommendations derived from this study.

Figure 2. Speech-to-noise ratio of amplified teachers, unamplified teachers, and students

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354 C. Y. Choi and B. McPherson

High Ambient Noise Levels and Effects on Students and Teachers

The levels of ambient noise found in the classrooms were unacceptably high, withthe average noise levels reaching 60.74 dB (A) and maximum levels of 67 dB (A)recorded. The recommended noise level for an occupied classroom should notexceed 40–50 dB (A) (Berg, 1993; Finitzo-Hieber, 1988). None of the Hong Kongclassrooms met the recommended level. When compared with the findings in theinternational literature the result obtained was not surprising. The typical ambientnoise level in occupied classrooms in the United States is also reported to be 60 dB(A) (Berg et al., 1996).

The presence of high ambient noise is a negative factor in the acoustical environ-ment of the classrooms. As mentioned earlier, noise adversely affects speech percep-tion, learning, reading, writing, spelling, attention, concentration, and theparticipation of students, especially young children, in primary schools. In addition,as an increasing number of children with special educational needs (e.g., studentswith hearing impairment) integrate into ordinary primary schools, the need to provide

Table 2. Absolute differences of test-retest measurements obtained in eight classrooms

Absolute difference between Visit 1 and Visit 2

Measurement Mean SD Range

Noise levelsdB (A) 0.70 0.49 0.10–1.37dB (SPL)

0.5 kHz 0.87 0.71 0.03–1.871 kHz 0.89 0.81 0.10–2.772 kHz 0.74 0.92 0.07–2.834 kHz 0.69 0.69 0.07–1.77

Speech levels (dB (A))Teachers

Amplified 0.95 0.49 0.60–1.30Unamplified 1.54 0.69 0.13–2.20

StudentsMale 1.05 0.70 0.20–1.93Female 1.87 1.35 0.53–3.93

Speech to noise ratios (dB)Teachers

Amplified 1.20 0.61 0.77–1.63Unamplified 1.19 0.63 0.10–2.06

StudentsMale 1.51 0.77 0.26–2.73Female 1.76 1.60 0.24–4.94

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an optimal learning environment is further highlighted, because such children aremost likely to be affected by poor classroom acoustics (Nelson & Soli, 2000). Noisealso compromises teacher performance through interference in speech and teaching,and may contribute to voice problems in teachers as they tend to raise their vocaloutput to compete with the high noise level present in classrooms (Sapienza et al.,1999; Smith, Gray, Dove, Kirchner, & Heras, 1997).

Low-frequency Noise Present in Classrooms

Results from this study indicated that Hong Kong classroom noise was predomi-nantly low frequency in nature, similar to previous findings in other school localities(Crandell & Smaldino, 1994; Crandell et al., 2004). The presence of low-frequencynoise imposes a greater adverse effect on speech perception than high-frequencynoise. Low-frequency noise tends to be a more effective masker because of itsupward spread of masking on the speech signal (Crandell et al., 2004). Hence, low-frequency noise can effectively mask teacher speech and thus reduce the speechrecognition abilities of students in classrooms.

Prolonged Excessive Voice use by Teachers

Findings of the present study indicate that the average speech level of teachers inclassrooms without the use of amplification was 73.32 dB (A). All of the teachers inthe present study had speech levels over 65 dB (A), which is the speech level in anormal conversation (Crandell & Smaldino, 2000a). One of the possible reasons forthe high speech levels of teachers obtained in this study is that the teachers tend toincrease their volume in order to overcome the effects of high ambient noise and tomaintain a speech level they considered audible by all students in the classroom(Nelson & Soli, 2000; Sapienza et al., 1999).

The high speech level of teachers is a favourable factor for the speech perceptionof students in classrooms as it can, to a certain extent, compensate for high back-ground noise levels. However, as noted earlier, teachers are more likely to have vocaldisorders as a result of the prolonged and sustained increase in vocal output for theschool day. The commonly associated voice symptoms are hoarseness, problemswith high-note singing, voice fatigue, weak and effortful voice, and difficulty withlow-tone speech (Smith et al., 1997).

Unfavourable Speech-to-noise Ratios for Students

The present study revealed that teacher speech was sufficient enough to be heard inmost classrooms, as 30 (85.71%) of the unamplified and all of the amplified speech-to-noise ratios of teachers reached the acceptable level of +10 dB for normal hearingchildren. However, the ideal level of at least +15 dB could rarely be achieved with-out the use of an amplification system. Only 25.71% of the unamplified teachers,but 75.00% of the amplified teachers, had speech-to-noise ratios exceeding +15 dB.

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The results of this study also highlighted the considerable barriers to listening thatstudents and teachers face in most classrooms. Among the 94 students sampled nine(9.57%) gave negative signal-to-noise ratios, and these were unfavourable levelseven for adult listeners (Crandell & Smaldino, 2000a). Only three samples (3.19%)resulted in speech-to-noise ratios exceeding +10 dB, which is the acceptable level fornormal hearing students. None of the speech-to-noise ratios of students reached themost favourable level for all listeners of +15 dB. The results revealed that studentsmay frequently be unable to listen clearly to the voices of their peers during lessons,such as when they are having presentations, discussions, sharing of ideas, and read-ing aloud. This implies constraints in student abilities to learn through interactionwith other students. It must also be remembered that this study measured speechand noise levels at one location only within each classroom. Any students seatedfurther from the teacher than the 2 m measurement location would be likely to havean even more unfavourable speech-to-noise ratio than those measured. Both theASHA (2005) and American National Standards Institute (2002) guidelines recom-mend a +15 dB speech-to-noise ratio at all locations throughout the room.

Inadequate Acoustical Treatments for Noise Reduction in Classrooms

This survey revealed that it was not uncommon for present-day classrooms in HongKong primary schools to exhibit inadequate acoustical modifications for the reduc-tion of noise. Only four (8.51%) of the classrooms had double-glazed windows andnone of the rooms exhibited the use of acoustically modified furniture, partitions,drapes or acoustically treated Venetian blinds, acoustic ceiling tiles, or carpeting,which are those acoustical treatments most effective in noise reduction (Crandell &Smaldino, 2000a).

The use of acoustical treatments such as double-glazed windows for minimisingthe external noise levels of classrooms is suggested, as they can effectively provideabsorption and interference of the noise outside the school building. However, justfour (8.51%) of the classrooms in this study exhibited the use of double-panedwindows; the remaining classrooms had a large number of single-paned windowsfacing outside walls. Some had open windows that faced potentially high externalnoise sources, such as busy streets.

Carpeting is effective for reducing room noises, such as the noise of shuffling ofhard-soled shoes and sliding of desks and chairs (Crandell & Smaldino, 2000a).However, none of the classrooms exhibited installation of carpet on concrete floor.Metal blinds were used in most classrooms (91.49%) but effective window treatmentsfor reducing room noise, such as draperies, thick curtains, or acoustically treatedVenetian blinds, were not used. The unpopularity of using carpets and drapes inclassroom settings in Hong Kong (and in the West) may due to the high cost involvedin maintenance and in cleaning these treatments. Acoustical ceiling tiles, which canprovide uniform absorption of noise at different frequencies, are the most commonlyreported acoustical treatment in Western classrooms (Rosenberg et al., 1999).However, none of the classrooms in this study used such ceiling treatment.

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Noise Levels in Primary Schools 357

It was interesting to note that 25 classrooms (53.19%) used closed windows andair-conditioning as a means to minimise the external noise, such as noise from anearby road. However, the use of air-conditioning for ventilation instead of openwindows will generate a significant amount of internal noise for classrooms,especially when these wall-mounted units are malfunctioning. Moreover, fans andventilators were present in all and 25 (53.19%), respectively, of the Hong Kongclassrooms. Improper functioning of these ventilating systems is another majorsource of classroom noise (Siebein, Gold, Siebein, & Ermann, 2000). Regular main-tenance for the air-conditioning and ventilating systems is essential for reducingclassroom noise.

Apart from the inadequate acoustical treatments presented in the classrooms ofthis study, four (8.51%) of the classrooms exhibited the use of thin wood partition ortemporary walls for the separation of the classrooms from adjoining classrooms. Apoor acoustical environment may result as significant sound transmission betweenrooms is possible in such situations.

Use of Classroom Amplification Systems

Results of the present study indicated a high ambient noise level with inadequateacoustical modifications in classrooms. Teachers had to raise their vocal outputappreciably to maintain a favourable speech-to-noise ratio for students, whilestudents were usually incapable of optimally listening to their peers. Hence, it issuggested that the use of SF amplification systems may be one of the most feasiblemeans for improving the acoustical environment in Hong Kong classrooms.

Students show improvement in academic achievement, speech recognition skills,attention, and participation with the use of SF amplification systems (Crandell &Smaldino, 1996; Massie et al., 1999; Rosenberg et al., 1999). Results in the presentstudy revealed an adverse student-to-student listening environment. Through thecirculation of a SF system microphone during classroom activities such as question-asking or question-answering, reading aloud, and oral presentations, students couldachieve improved speech-to-noise ratios and hence more effectively participate inthe classroom. Furthermore, SF amplification could also assist teachers in HongKong primary classrooms, all of whom in this study were using a greater thannormal speaking level. The use of an amplifying system can reduce the likelihood ofteacher voice problems. Teachers would no longer need to raise and sustain theirvoice for prolonged periods of time to maintain speech audible by all students. SFamplification is the most inexpensive and cost-effective way of improving the acous-tical environment in classrooms (Crandell & Smaldino, 2000a).

The results of the present study showed a statistically significant increase inspeech level and speech-to-noise ratios of teachers—by 8.62 dB and 4.92 dB,respectively—with the use of amplification systems. The results reflected an antici-pated +5 to +10 dB enhancement that such systems are usually estimated toprovide. However, this study revealed that the use of SF amplification systems inclassrooms of Hong Kong primary schools was not widespread. Among the 47

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classrooms, 18 of the rooms were equipped with fixed public address amplificationsystems (Super-sonic UA-805 PA amplifier), with only 10 systems (21% of class-rooms) in use during the present survey. In another two classrooms (4.26%), teach-ers used a compact, battery-powered, portable amplification system (Super-sonicUA-803 portable amplifier). No classrooms were equipped with multi-speaker SFamplification systems that would optimally enhance the acoustic environment.

However, the use of an amplification system can be annoying when the ambientnoise level of a classroom is already high (Nelson & Soli, 2000). Furthermore, a highspeech-output level may transmit unwanted noise to adjacent classrooms rooms whenthere are insufficient sound barriers between rooms. Students may also need to raisetheir vocal output in order to be heard by their peers in such an environment.

Limitations of the Present Study

There are several limitations in the present study that need to be identified. Firstly,the number of classrooms participating was relatively small compared with the totalof 819 government primary schools in Hong Kong and further studies conductedwith larger sample size are warranted. Secondly, the occupied noise level wasmeasured when both teachers and students were relatively quiet. Hence, more repre-sentative measurements could be taken to gauge speech-to-signal ratios duringverbal, instructional teaching (Massie et al., 1999). Thirdly, the speech levels ofstudents were measured while they were reading aloud a short text passage. This isnot the most representative and commonly occurring speech activity in a classroomsetting. Instead, the speech level of students in response to a question from theteacher or commenting on the contribution of peers could be measured.

Moreover, the present study provided measures of occupied classroom ambientnoise level. Further studies measuring the unoccupied noise level of classroomswould enable results to be directly compared with the recommended level of unoc-cupied noise level as suggested by the ASHA (2005). Through comparing the unoc-cupied and occupied noise levels, it can be determined whether the high ambientnoise level is due to external noise or to noise generated within the room.

Finally, further studies are needed to investigate other acoustical variables, such asreverberation time and speaker–listener distance, which also impose negative impactson the acoustical environment in classrooms. This is because the interaction betweennoise and reverberation synergistically affects speech perception in classrooms(Finitzo-Hieber & Tillman, 1978) and it is common to find high reverberation timesin classroom settings (Crandell et al., 2004).

Conclusion

Classroom acoustics can have great impact on speech perception, academic achieve-ment, and the participation of students, and may contribute to teachers’ perfor-mance and vocal hygiene. Many Western investigations have noted the negativeimpact and the widespread prevalence of high noise levels and poor speech-to-noise

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Noise Levels in Primary Schools 359

ratios in classroom settings. Results from this Hong Kong study revealed a similarlyhigh background noise level and the predominance of low-frequency noise in class-rooms that may affect the learning and listening of young students. Excessively loudvoice was found to be used by teachers, and this may contribute to their likelihood ofhaving or developing voice problems. Lack of appropriate acoustical treatments inHong Kong primary school classrooms was apparent. The most cost-effective way ofproviding a more favourable classroom listening and speaking environment isthrough the use of SF amplification systems by both students and teachers. Furtherinvestigations that examine the acoustic environment in primary schools in highlyurbanised environments such as Hong Kong are warranted.

Acknowledgements

Sincere thanks are extended to Ms Christine Ng for her generous assistance in theschool recruitment process, and to the reviewers and editorial team for their feed-back on this article.

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