*Loudness Perception

acceptable noise level (ANL) is

the individuals most comfortable speech level (MCL) minus his/her max acceptable background noise level (BNL) for speech

Stevens proposed the sone as a unit of loudness where 1 sone is defined as

the loudness of a 1k Hz tones at 40 dB SPL A 1K Hz tone of 50db SPL is judged as twice as loud as a 40 db tone (2 sones) at low levels, loudness changes more rapidly than predicted

Aided ANL

using the same protocol as that used for the unaided ANL, an aided ANL score is obtained. The diff btwn scores is the benefit of the noise reduction strategies implemented by the HA

increment detection:

-a steady state stimulus is presented and an increment in level is superimposed on the steady state stimulus -subj indicates interval with increment

ANL protocol

-establish MCL for speech (recorded story or running speech) - present speech background noise and establish max acceptable level (BNL) highest level subject is willing to "accept or put up with" in presence of speech -ANL=MCL-BNL

Modulation detection

-stimulus is amplitude modulated in one interval & unmodulated in the other interval -subj indicates interval with modulation

intensity discrimination

-two gated pulses of sound differing in intensity are presented in succession -subj indicates which interval contained the more intense signal

Human ear is capable of responding to a range of intensities from about

0dB SPL -140dbSPL, which corresponds to a ratio of 100,000,000,000,000:1

higher freq show 1.___ with broadband noise 2.___

1. (</= 4KHZ) show greater fatigue effects 2.max TTS occurs in the 4-6kHz freq region

Loudness of complex sounds: Ear "considers" all energy in 1.__ When frequencies exceed 1 CB 2.___

1. CB together as 1 sound, so loudness is proportional to total intensity of sound in the CB 2. more than 1 CB contributes to loudness and loudness increases even though the total intensity is unchanged

Clinical measures:_____ influenced by___?

1. MCL 2. UCL 3. tested with tones or speech 4. influenced by stimulus, test method and instructions

aud fatigue: it refers to 1.___ post stimulatory aud fatigue is also often referred to as 2.___

1. a change in responsiveness from stimulation which is more intense than required for a "normal" physiological response, and is measured after the stimulus is terminated (post stimulatory) 2. temporary threshold shift (TTS)

pathological adaptation: abnormal aud processes can result in 1..____ which differential diagnostic clinical tests have been used to examine this phenomenon?

1. a rapid decrease in neural responsiveness 2. tone decay and difference in thresh for continuous & interrupted tones

what did Scharf find in his review of loudness adaptation?

1. adaptation occurs only for low level (i.e.<30dbsl) tones 2. HF's adapt more than LF's 3. steady sounds adapt more than modulated sounds 4. individuals differ widely in adaptation

Loudness recruitment is 1.___ how is it tested? 2. __

1. an unusually rapid growth of loudness in ears with cochlear pathology as the level of a tone increases 2. tested via alternate binaural loudness balance (ABLB) test or monaural loudness balance (MLB) test

What mechanisms are involved in intensity discrimination? *explanations

1. changes in neural firing rates at center of excitation pattern and spread of excitation pattern 2. phase locking of neurons *central mechanisms may limit intensity discrimination

Hearing protection

1. earmuffs: largest form of hearing protection that fit over the ears & generally provide good protection 2. earplugs: several types that give diff degrees of protection. More expensive ones allow you to communicate freely even while wearing them 3. both: for extremely noisy situations. This gives the greatest amount of protection

Loudness adaptation: sensory sys chnage responsiveness with 1.___ Auditory adaptation refers to 2.___

1. extended exposure; this may occur during or after the stimulation 2. the decline in response over time of a receptor to a steady stimulus *early research used loudness balance tests to study auditory adaptation

aud fatigue generally 1.___ For low freq 2.____

1. increases with exposure duration 2.(particularly for noise or rapidly interrupted tones) growth rate is reduced (ME reflex?)

Although TTS generally decreases with 1.___ the shape of the function suggests that 2___

1. increasing recovery time, recovery from TTS immediately after exposure is often followed by a "bounce" particularly at HF's 2. there are 2 processes involved: short term recovery process corresponding to neural activity, and a longer term process related to hair cell and metabolic changes *take a look at exposure hours*

TTS generally increases with 1.___ At low intensities, TTS 2.___

1. intensity of fatiguing stimulus 2. changes slowly as a function of intensity and only occurs for test tones with freq close to the fatiguing stim *with increasing intensity, TTS increases and freq range of effect increases

post stimulatory aud fatigue: factors influencing the size of TTS

1. intensity of fatiguing stimulus 2. duration of fatiguing stimulus 3. frequency of fatiguing stimulus 4. frequency of test stimulus 5. time btwn cessation (stop) of fatiguing stimulus and thresh measure-recovery interval

Implications: Auditory sys can detect changes in 1._____ Webers law holds for 2.___

1. intensity over a wide range (approx 120dB) 2. noise bursts, but discrimination of pT's improves with increasing sound levels (to about 100dB SPL)

Temporal integration of loudness: just as absolute thresh is affected by duration...1__ In general loudness ___ with durations ____

1. loudness perception is also affected by duration 2. increases with duration 100-200ms

How many pple under 18 have HL?

1.3 million americans that can be attributed at least partly to noise exposure. The degree of loss is comparable to that which we see for pple in their 40s and 50s *60% of members in rock & roll hall of fame have impaired hearing

What's the standard tone of the phone scale?

1000Hz. A 1k HZ tone of 40dB SPL has a loudness level of 40 phones. *a comparison tone judged to be =ly loud to a 1k HZ tone of n dB SPL is said to have a loudness level of n phons.

Application: Weighting of sound level meters

A scale weighting is based on 30-40 phon contour B weighting based on 70 phon contour C weighting is more linear (similar to SPL)

Can loudness be measured directly?

It cant be measured directly, but can be ordered on a scale from soft to loud

what are 2 popular methods that attempt to derive scales relating the physical magnitude of sound to its subjective loudness: *early work conducted by SS stevens

Magnitude Estimation: subj assign #'s to sounds of diff levels according to their perception of the loudness of the sounds Magnitude Production: Subj adjust the levels of sounds to achieve particular loudness levels, either absolute or proportional (ex, 1/2 or 4 times)

What technique are often used to measure loudness?

Magnitude estimation, magnitude production and loudness matching

the lower freq grow in loudness at

a faster rate than the higher frequencies * so the relative loudness of diff freq components of a complex change as a function of overall level

intensity discrimination is.... technique & thresh defined as?

a measure of the smallest detectable change in intensity; technique is often 2AFC and thresh is usually defined as 75% correct level

Loudness is _____ that depends on___

a subjective equality that depends on sound pressure level, but also on freq, duration, & amplitude envelope

aided sound quality

at a comfotable listening level (4 on the IHAFF loudness scale) the client rates a passage of music or speech on the following dimensions of sound quality from 0 (very poor) to 100 (very good) -clearness -sharpness -fullness -overall impression

adaptation: According to Hood ('72) auditory adaptation differs from auditory fatigue in that

fatigue "results from the application of a stimulus which is usually considerably in excess of that required to sustain the normal physiological response of the receptor, and is measured after the stimulus has been removed

intensity detection

generally similar but some diff can be seen: For wideband or bandpass-filtered noise, the smallest detectable intensity change is nearly a constant fraction of the intensity of the stimulus (ΔI/I is roughly a constant); in db, is about .5 to 1.0 (20-100 dbSL) *for PT's we see a "near miss" to webers law (discrimination improves at high levels)

Application: Contours explain why

human voice sounds "boomy" though loudspeakers (ear is more sensitive to low freq at higher levels)

Adaptation: newer studies show more or less adaptation than early studies?

less

In cross modality matching (CMM)

listeners use the visual modality to make loudness judgment measures

Loudness level contours: The lower level curves follow the

minimum audibility curve, but the higher level curves show a "flattening" (similar to the thresh of feeling)

Detection of intensity changes: 3 methods used

modulation detection, increment detection, intensity discrimination

Loudness scaling: Stevens suggested that loudness (L) was a

power function of intensity (I), such that L=KI^0.3, where k is a constant or approx. a 10 fold change in intensity (10 dB increase) produces a 2-fold change in loudness

Loudness scaling: Techniques are subject to a # of confounding influences such as....1.___ Subjects also show...2___ When bias effects are excluded, it appears that

range of stimuli, first stimulus, instructions, allowable range of responses, (other...) 2. a wide range of differences 3. loudness doubles with 6 db increases * despite criticisms we often want to know how loudness is perceived by people

in categorical loudness scaling

signals are presented at different intensity level and subj are asked to judge the perceived loudness on a 5-7 point scale from not heard or very soft to extremely or uncomfortably loud

the curve is known as

the = loudness level contours or the fletcher-Munson curves

loudness models: mechanisms & processes of loudness perception are not fully understood but are believed related to

total neural responses (summed neural activity across critical bands)

Aided LDL

with client seated 1m from the loudspkr aided loudness judgements are made on several common noises delivered at 85dBA. ratings should be at #5 or 6 on IHAFF scale