2.05: Environmental Acoustics Flashcards by Sheri Robertson

What are the 4 factors that influence communication difficulties?

Speaker
Message
Environment
Listener

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What are the 3 Acoustical Barriers to Learning?

Noise
Distance
Reverberation

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What is the criteria for noise in a classroom?

Should not exceed 35 dBA in classrooms of 20,000 cubic feet or less

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What is the criteria for Reverberation Time in a classroom?

Should be .4 sec- .6 sec unoccupied

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What is the criteria for SNR in a classroom?

Should be at least +15 dB at the child’s ears

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Speech perception is affected by what 4 variables?

Noise
SNR
Reverberation
Distance

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What is the worst kind of noise that can impact speech perception

Speech! Speech has same spectra, so it will mask the speech signal

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Types of Classroom Noise (3)

External Noise
Internal Noise
Room Noise

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What have typical classroom noise levels been measured at?

Mean Noise Level: 51 dBA
Range: 46-59

Unoccupied recomendation: 35 dBA

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Relationship between the intensity of the signal and the intensity of the noise

SNR

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Which is a more favorable SNR: +5 SNR or -5 SNR?

+5 SNR. Positive SNR indicates a more favorable listning environment

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What is a typical SNR for a small group conversation?
For a car?
For a classroom?
For a restaurant?

Convo +3
Car 0
Classroom +5 to -7
Restaurant -5

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A greater _____________ is needed with Sensorineural Hearing Loss.

SNR

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What SNR is needed for individuals with SNHL?

+5 to +10 in non-reverberant rooms
+8 to +16 in moderately reverberant rooms

(Overall, at least +15)

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T/F: +15 SNR should be easy to accomplish.

False.

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What is HINT?

Hearing In Noise Test

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At what level is the noise set for a HINT?

65 dBA

Who requires a more favorable SNR, Children or Adults?

Children require a better SNR.

What is the AI? What does it represent?

Articulation Index; Represents Audibility of sounds in the presence of background noise

Why can adults get away with a lower AI?

Adults can get away with less audibility because contextual/life experience helps them fill in the blanks. Also, the Precedence Effect is not as developed in children (ability to suppress reverberant sounds).

What is the Precedence Effect?

One’s ability to suppress echo-like sounds that arise from sound bouncing off reflective surfaces.

What SNR do normal hearing children require for optimum auditorycomprehension?

+6 SNR

What SNRs have been reported in typical classrooms?

+5 to -7 SNR

Besides SNR, what additional factors can affect children’s auditory comprehension?

Reverberation 
Distance 
Level of HL 
ELL 
Learning Disabilities, Attention Problems

What is the problem with hearing aids in noise?

Hearing aids amplify everything, including noise. Directional microphones can help improve SNR.

Term used to describe the phenomenon of sound reflection; the prolongation of sound waves within a room as they are reflected off hard surfaces

Reverberation

The amount of time it takes for a loud sound to decrease so it is inaudible

Reverberation Time

Why is RT a problem?

Reflected sound masks direct sound. Reverberation causes prolongation of the spectral energy of vowels, which masks consonants.

T/F: Reverberation mean decreased speech understanding for HI individuals only.

False. It can affect people with normal hearing as well.

Individuals with what type of HL are affected even more adversely by reverberation?

SNHL

Reverberation alone severly _____________ the signal, even without any ___________________.

smears; background noise

What is the ideal RT for a classroom?

larger classrooms: .6 - .8 seconds | smaller classrooms: .4 seconds

What is the inverse square law?

SPL decreases 6 dB each time distance is doubled. (sound fades rapidly as distance increases)

What is Critical Distance?

The distance from the sound source at which the intensity of the direct signal is equal to the intensity of the reflected signal.

Students with HL should sit within _______________________ ______________.

Critical Distance

Why is "preferential seating" not enough for ensuring good speech perception?

If the seating is not within the Critical Distance, it will make little difference.

Three Criteria for Classroom Acoustics

Noise: should not exceed 35 dB SNR: should be +15 or better RT: should be .4-.6 unoccupied Children who are D/HH must be seated within CD

What are the three places where we can imporve classroom acoustics?

External Noise- locating of school, quiet area, double-paned windows, good doors, etc. Internal Noise-Insulate hallways for noise, no ventilaltion ducts in hallways, locate D/HH classrooms away from noise sources Room Noise- Acoustic treatments, reduce background noise, seat D/HH student away from noise, preferential seating, small groups, ALDs

What are ways to improve speech access in classrooms?

Use ALDs Improve visual cues Avoid behaviors that make face difficult to see clearly

T/F: ALDs are for HI kids only.

False. Assistive technology can be used for normal hearing kids