Assistive Listening Technology:in the workplace and on campus

Jeremy Brassington

Tuesday, 11 July 2017

Why is it hard to hear in noisy rooms?

• Distance from sound source

• Background noise – continuous and intermittent

• Reverberation

• Individuals find it hard to hear what is said and lose concentration

• Audibility and comprehension are not the same – hearing without understanding

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Distance:The inverse square law

The sound intensity from a point source of sound will obey the inverse square law if there are no reflections or reverberation.

A plot of this intensity drop shows that it drops off rapidly.

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Background Noise

• Continuous - traffic, equipment noise, other conversations or telephone calls etc

• Intermittent - coughing, door slamming, sirens

• Compete with the voice of the speaker

• Noise levels in classrooms and lecture halls –60 to 70dB

• Noise levels in open plan offices - 35 to 55dB

• Typical spoken voice range between 50 and 65dB

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Reverberation

• Original sound shown in red

• Reverberant sound shown in green

• In this example the reverberant sound is masking the consonant peaks

• The greater the reverberationin the room the lower the speech intelligibility

Original sound Reverberant sound

Cumulative effect

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• In combination will lead to lower speech intelligibility

• Impaired Aural Focus makes it difficult to hear one sound out of several

• Loss of a key word can make a sentence meaningless

• Lose concentration

• Performance will suffer

Why do hearing aids not solve the problem?

• High speech to noise ratios required

• Quality of sound arriving at hearing aid microphone

• Hearing aids can amplify and process sound signals to match hearing loss

• Cannot replace missing words or syllables

• Physical position of microphone

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Challenges in the workplace and on campus

• Meetings and workshop groups

• Telephone conversations

• Conferences and courses

• Interaction with customers in retail environments

• Conversations in noisy open plan offices

• Note-taking in lectures and meetings

• High noise level environments which compete with the volume level of the speaker

• Low speech to noise ratio

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Effects of hearing loss

• Resort to lip reading

• Increased stress levels where cannot hear properly

• Reduced understanding if words unclear

• Extra effort to communicate and learn

• Reluctance to admit lack of hearing

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What is the solution?

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• Use Assistive Listening Technology to amplify the speaker’s voice and separate it from the ambient noise

• Deliver the speaker’s voice directly to the person using a hearing aid or headphones /earphones

• Eliminate distractions allowing individual to focus on speaker’s voice

Assistive Listening Equipment requirements

• Capture the speech signal

• Deliver that signal to the individual with hearing loss

• Amplification

• Strong signal to noise ratio

• Good directionality

• Low distortion

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In combination these will enhance the speech to noise experience of the individual and improve comprehension ability

Different Types of Assistive Listening Technology

• Inductive Room Loop

• Amplified Listeners

• Wireless Assistive Listening Devices (“ALDs”)

• Note-taking solutions and Directional Microphones

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Inductive room loop

• Loop of wire encircles listening area connected to amplifier output of sound system

• Hearing aid acts as the “receiver” through the Telecoil setting

• Fixed installation

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Only used for individuals who are wearing a hearing aid. Not portable from room to room.

AmplifiedListeners

• Directional microphone and sound amplification

• Can be used with hearing aid or headphones/earphones

• Speaker’s voice is amplified but any noise between speaker and listener will also be amplified

• Listener needs to be close to speaker or in a small room

• Can be used to amplify telephone conversations

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Limited to use in one to one or small meeting rooms and telephone amplification

WirelessALDs

• Wireless ALDs use a microphone transmitter which is worn or held by the speaker –FM Radio, Infrared or Bluetooth devices are available

• The speaker’s voice is broadcast to one or more receivers worn by the hearing impaired employee

• Individual listens to speaker’s voice through hearing aid or headphones/earphones

• Dramatically improves speech to noise levels and increases speech intelligibility

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Most suitable type of system for hearing impaired individuals in meeting rooms, conference halls and noisy environments.

FM Radio Systems

• Speaker’s voice is broadcast to one or more receivers worn by the individuals who need hearing assistance-like a one way walkie-talkie

• Individuals listen through hearing aid or headphones/earphones

• Range of up to 50m indoors and up to 100m outdoors –suitable for large venues

• Can be connected to TV or sound system

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Tried and tested reliable system of communication for the hearing impaired user.

Bluetooth Systems

• Wireless bluetooth available for connectionto mobile phones, computers and TVs

• Limited range so not ideal for large rooms

• Higher battery usage

• Some latency issues with lip reading and sound transmission not synchronised

• Expensive

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Used for small groups where connection to TV, mobile phone and computers is important.

InfraredSystems

• Speaker’s voice is broadcast to one or more receivers worn by the individuals who need hearing assistance using Infrared signal-like a TV controller

• Individuals listen through hearing aid or headphones/earphones

• Cannot be used where there are obstructionsor partitions in the lecture hall

• Not suitable for outdoors or large venues

• Can be connected to TV or sound system

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Used for small groups indoors where there are no obstructions. Most often used as TV listeners.

Note-takingSolutions

• Use DVR or recording App and directional microphone

• Note-taking software to edit and collate notes

• Remote notetaking assistance

• Matching notes to audio recording

• Reduce stress

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Used by hard of hearing and individuals with SpLDs at university

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Summary

High ambient noise leveland poor room acoustics

Position of the microphone is key

Wireless microphones can improve intelligibility

Note-taking solutions can improve understanding

Inclusion

Stress reduction

Thank you

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