Quiz 4 Sense of Hearing

What is the most common difficulty among people who have hearing loss?

Hearing in noise.

Common for a person with hearing loss to listen comfortably in quiet conditions.

Noise has disproportionate impact when the listener has sensorineural hearing loss.

What is the cocktail party effect?

Ability to focus your attention on a single sound source.

Based on:

• Spatial location

• voice pitch

• intensity (louder or softer)

Signal-to-noise ratio

the ratio of signal intensity to noise intensity

the severity of background noise is expressed as this.

Positive SNR

means the intensity of the signal is greater than the intensity of the noise.

• signal 70 dB—> Noise 65 dB= SNR is +5dB

0 dB SNR

means the intensity of the signal is the same as the intensity of the noise

• Signal 65 dB—> noise 65 dB= SNR is 0 dB

Negative SNR

means the intensity of the signal is less than the intensity of the noise

• Signal 65dB—> noise 70 dB= SNR is -5 dB

How to calculate the SNR

What appears to be a simple difference between decibel levels is actually a ratio because decibels are multiplied.

Why does sensorineural hearing loss make speech difficult to seperate from noise?

NOT merely because of reduced audibility: if it were then we’d observe difficulty in noise among people who have conductive hearing loss.

It’s mainly because of the distortion of sound resulting from damaged OHC—> this should make sense because OHCs sharpen our frequency differences.

White noise

equal energy at all frequencies.

Never used as a masker for real experiments and evaulations

Pink noise

equal energy at all octaves/more energy at low frequencies

Commonly used for real evaluations or experiments

Because it nicely reflects the natural distribution of sound energy encountered in the world.

Speech-shaped noise

long-term spectrum is the same as speech

averages the spectrum of a long stretch of speech and filters noise to have that same spectrum.

But unlike speech, it is steady in loudness (no modulations), no intelligible words (no information), and is not harmonic (no pitch)

What noise should you use to make sense of noise when it is used to represent a long chunk of speech?

speech-shaped noise

What kind of intensity does speech tend to have in a long-term sense?

Greater intensity in the low-frequency region (below 1500 Hz) which slopes down to reduced intensity in the higher frequencies.

What phonetic features are affected by noise?

Voicing: still perceivable at nearly 100% accuracy even when there is background noise.

Manner of articulation: t-s, d-z, p-f, sh-ch,= mostly still perceptible when there is background noise. Some mistakes.

Place of articulation: t-k, d-b, s-f, n-m,= most often misperceived when there is background noise. So many mistakes

Single talker

harmonic (it has pitch contour), it could contain energy that will overlap with the target speech, in terms of frequencies and modulations.

What is easier to hear a single talker with what kind of vocal tracts?

High F0= smaller vocal tract

Low F0= larger vocal tract

Why would you want speech shaped noise?

when you want a background noise that mimics the dynamic modulations of speech, offering the opportunity to glimpse the target speech.

But you don’t want to introduce complicated confusions by accidentally introducing real words.

Multi talker babble

similar to competing talker but key differences are:

not intelligible (less potential for intrusive confusing information)

Modulations (fluctuating soft/loud moments) are weaker, because the moments of silence for one talker are filled in with vocal parts from a different talker.

energetic masking

physical interference of the masker on the signal

when both sounds contain energy in the same frequencies at the same time and portions of the speech signal are rendered inaudible at the periphery

overlap in the ear

informational masking

confusions (uncertainty) b/w signal and masker

when the signal and masker are both audible but the listener is unable to disentangle the elements of the target signal from a distracter based on similarities or attentional patterns.

Confusion in the brain

Does turning up the volume up for conductive hearing loss an easy way to manage audibility?

yes

when something is obstructing the path of the sound but the cochlea (OHCs, nerves) are healthy

they provide straight amplification and difficulty is relieved.

Sensorineural hearing loss has loss at what regions?

loss is usually high frequencies

Want to amplify the higher frequencies not the lower ones but because the lower ones are also getting loud it is masking the higher frequencies. (this is a typical hearing aid design)

What is a typical challenge with amplifying high frequencies in hearing aids?

FEEDBACK Cancelation: hearing aids have special ways to detect their own output in an attempt to cancel feedback before it loops back into the microphone

Like when you cup your hand.

Hearing aids must provide more intensity boost to sounds that are soft but less to ones that already loud.

Damaged OHCs means poor frequency tuning

means expanding the range of the cochlea that is activated.

• this causes lack of clarity in the sound (even if it is amplified)

• Also happens when sound intensity is increased (leading to an increase in perceived loudness)

  • meaning loud sounds can sound very loud to a person with sensorineural hearing loss (loudness recruitment)

Speech-shaped noise has more energy in the:

low frequencies

This type of hearing loss usually results in difficulty hearing speech in noise

Sensorineural