HIS 230 - Audiometry Masking Rules

Audiometry Masking Rules Audiometry Masking Rules

Air conduction masking ruleAir conduction masking rule

Mask when there is a forty decibel Mask when there is a forty decibel difference between the air difference between the air conduction threshold of each ear, or conduction threshold of each ear, or the better ear’s bone conduction the better ear’s bone conduction threshold.threshold. Start masking level in the Start masking level in the non-test non-test earear at ten decibels greater than its at ten decibels greater than its air thresholdair threshold. (NTE dbHL + 10dbHL).. (NTE dbHL + 10dbHL).

Audiometry Masking RulesAudiometry Masking Rules

Bone conduction masking ruleBone conduction masking rule

Mask bone results when there is a Mask bone results when there is a fifteen decibel difference between fifteen decibel difference between the better ear bone score and the the better ear bone score and the poorer ear air score.poorer ear air score. Start masking level at ten Start masking level at ten decibels greater than the decibels greater than the non-test non-test earear air thresholdair threshold. (NTE dbHL . (NTE dbHL +10dbHL).+10dbHL).


Bone conduction maskingBone conduction masking

Remember, masking noise greater Remember, masking noise greater than forty decibels may result in than forty decibels may result in over-masking.over-masking. This is very important when This is very important when masking for masking for bone conductionbone conduction..


Speech masking RuleSpeech masking Rule

Mask speech results when there Mask speech results when there is a forty decibel difference is a forty decibel difference between SRTs of each ear; or, a between SRTs of each ear; or, a forty decibel difference between forty decibel difference between the pure tone average (using the pure tone average (using either the best two frequency or either the best two frequency or three frequency PTA average) of three frequency PTA average) of air thresholds.air thresholds.


Speech Masking RuleSpeech Masking Rule

Use speech masking level in the Use speech masking level in the non-test ear at an intensity thirty non-test ear at an intensity thirty decibels less than the decibels less than the Presentation LevelPresentation Level of the test of the test earear. .

(TE PL-30dbHL = masking setting (TE PL-30dbHL = masking setting for NTE)for NTE)


PURE TONE MASKING NOTEPURE TONE MASKING NOTE With pure tone air and bone With pure tone air and bone

conduction testing, you will need to conduction testing, you will need to calculate and adjust the masking calculate and adjust the masking level for each frequency tested. level for each frequency tested.

You will set the masking level at You will set the masking level at each measured frequency based each measured frequency based upon the air conduction hearing loss upon the air conduction hearing loss in the NTE at that frequency.in the NTE at that frequency.

Audiometry Masking RulesAudiometry Masking RulesSPEECH MASKING NOTESPEECH MASKING NOTE

For speech masking, you will use a For speech masking, you will use a white noise or speech noise masking white noise or speech noise masking signal and mask one hundred percent signal and mask one hundred percent of the time. of the time.

The masking level should be based The masking level should be based upon the upon the presentation level presentation level to the to the test ear.test ear.

NOTE: You will not need to change the NOTE: You will not need to change the masking level for any of the following masking level for any of the following PB or Spondee word presentations.PB or Spondee word presentations.

Audiometry Masking RulesAudiometry Masking RulesHood’s Masking Plateau MethodHood’s Masking Plateau Method

(“Chasing the Rabbit”)(“Chasing the Rabbit”)

For air and bone conduction testing, For air and bone conduction testing, we will first determine the necessity for we will first determine the necessity for masking, then apply our masking rule. masking, then apply our masking rule. We will then begin the We will then begin the “chase”/search for each frequency’s “chase”/search for each frequency’s effective masking level effective masking level using Hood’s using Hood’s plateau method.plateau method.



For practical application in determining For practical application in determining the the effective masking leveleffective masking level; the ; the starting/beginning decibel level settings starting/beginning decibel level settings for the test ear and non-test ear are for the test ear and non-test ear are determined by the previously described determined by the previously described rules. rules. When those starting points have been When those starting points have been determined, the “chase” begins!determined, the “chase” begins!



Let’s review the worksheet Let’s review the worksheet keys on pages #49 & #50 of keys on pages #49 & #50 of Donaldson.Donaldson.



As you will notice, the test ear tone As you will notice, the test ear tone is increased in five decibel steps until is increased in five decibel steps until the “rabbit” appears. the “rabbit” appears. The “rabbit” is chased by the The “rabbit” is chased by the masking level (in five decibel steps) masking level (in five decibel steps) until the tone is no longer heard. until the tone is no longer heard.



If the masking level is increased three If the masking level is increased three times (at the five decibel increments), and times (at the five decibel increments), and the “rabbit” is still there (tone is still heard), the “rabbit” is still there (tone is still heard), the “rabbit” has been caught and the the “rabbit” has been caught and the effective masking leveleffective masking level has been has been achieved!achieved!This final This final effective decibel masking effective decibel masking levellevel should be noted upon the audiogram. should be noted upon the audiogram.


UNDERMASKINGUNDERMASKING This may occur whenever there is This may occur whenever there is

insufficient masking stimulus insufficient masking stimulus presented to the non-test ear. presented to the non-test ear.

It most often occurs during supra-It most often occurs during supra-threshold word recognition testing.threshold word recognition testing.


OVERMASKINGOVERMASKING This may occur anytime the This may occur anytime the

masking level used in the non-test masking level used in the non-test ear is greater than forty decibels. ear is greater than forty decibels.

It will most often occur during bone It will most often occur during bone conduction testing of the test ear.conduction testing of the test ear.


MASKING DILEMMAMASKING DILEMMA

This occurs most often when the This occurs most often when the bone conduction thresholds are bone conduction thresholds are within normal threshold limits for within normal threshold limits for each ear. each ear.

Audiometry Masking RulesAudiometry Masking RulesMASKING DILEMMAMASKING DILEMMA

A rule for identifying a masking dilemma, is A rule for identifying a masking dilemma, is to add the two air-bone gap decibel levels to add the two air-bone gap decibel levels together. together.

If their sum is greater than twice the IA If their sum is greater than twice the IA (forty decibels for standard headphones) i.e. (forty decibels for standard headphones) i.e. eighty decibels, then a masking dilemma will eighty decibels, then a masking dilemma will occur. occur.

This masking dilemma should be noted This masking dilemma should be noted upon the audiogram.upon the audiogram.


Let’s review some of the Let’s review some of the sample audiograms found on sample audiograms found on pages #57--#64 of pages #57--#64 of Donaldson to observe a few Donaldson to observe a few various masking various masking scenarios/situations.scenarios/situations.

Health & Medicine

HIS 230 - Audiometry Masking Rules