Masking And Speech Audiometry

Front 1

When we perform audiometry under certain circumstances, we need to mask. Why?

Back 1

- The technique of masking is used in order to isolate the test ear and ensure that results obtained are the true thresholds of the test ear.

- For air conduction if there is a 40 dB gap or greater between ears, you must mask those thresholds taking intramural attenuation into consideration.

- For bone conduction if there is a 15 dB gap or greater between air and bone conduction thresholds, then masking must be performed.

Front 2

Define and describe what central masking is and to what extent it may affect the thresholds we obtain.

Back 2

- Central masking refers to contralateral masking that can produce a small threshold shift in the test ear even when the making level is insufficient to produce overmasking. Central masking has been reported to influence thresholds measured during both puritan and speech audiometry. The shift is thought to be approximately 5 dB.

Front 3

What is inter-aural attenuation (IA)? How does it affect audiometry procedures, specifically our decision and process of masking? What IA values do we use, and why?; are the values different for air conduction and bone conduction and/or different transducers?

Back 3

- Interaural attenuation refers to the reduction of energy between ears. Its is the decibel difference between the hearing level of the signal at the test ear and the HL reaching the non test ear.

- If an air conduction threshold in the test ear minus the interaural attenuation (40 dB for supra-aural headphones, 70 dB for insert earphones) is GREATER than or EQUAL to the bone conduction threshold in the non-test ear, cross hearing is suspected and masking is needed.

Front 4

What types of masking stimuli do we use in audiometry and why? Be sure to include in your answer, at a minimum, the name of the stimuli, a description (spectral presentation), and why/how that particular stimuli was chosen.

Back 4

- White noise is a broadband stimulus that contains equal energy across a broad range of frequencies. Because of its broadband spectrum it has the ability to mask pure tone stimuli across a broad range of frequencies.

- Narrowband noise is typically the chosen stimulus for masking. It limits the confuse of the test signal and the masking noise.

- Speech spectrum noise is typically used as a masker during speech audiometry. Speech is a broadband stimulus that requires a broadband masker.

Front 5

Be familiar with the symbols used on the audiogram.

Back 5

O right (air unmasked) triangle (air masked)

X left (air unmasked) square (air masked)

> left (bone unmasked) ] (bone masked)

< right (bone unmasked) [ (bone masked)

Front 6

Write down the instructions you would give to someone before you begin a masking procedure.

Back 6

- So we are going to keep listening and responding for tones (whichever the test ear), but you are going to hear some noise/static in the opposite ear (non test ear). I want you to try and ignore that noise and focus on responding to the tones in the other ear.

Front 7

Discuss the relationship between efficiency and effectiveness of a masker (not the person, but the stimuli)....including the concept of critical bands would be a good idea.

Back 7

- The most effective masker (provides the most amount of masking for the least amount of energy because it is not efficient) for a pure-tone of the same frequency.

- The clinical goal is to select a masker that is efficient and that means that person produces a given effective level of masking with the least overall sound pressure level.

Front 8

What is the definition of threshold as it relates to speech audiometry?

Back 8

- The lowest stimulus level and the number of correct responses, that are then plotted on a psychometric function.

Front 9

What event (and who was involved) served as the basis for the creation of speech audiometry materials?

Back 9

- Speech audiometry developed originally out of the work conducted at Bell Labs in the 1920s and 1930s where they were looking into the efficiency of communication systems, and really gained momentum post World War II as returning veterans presented with hearing loss. The methods and materials for testing speech intelligibility were of interest then.

Front 10

When to mask pure-tone air:

if you have no BC:

How much masking:

Back 10

AC(test ear) - BC(NonTest ear) > 40 dB

AC(test ear) - AC(NonTest ear) > Interaural attenuation

minimal masking level = AC(NTE) + 10 dB

Front 11

When to mask bone conduction:

How much masking BC:

Back 11

air/bone gap > 15 dB

minimal masking level = AC(NTE) + OE + 10 dB

250 (20 OE) 500 (15 OE) 1000 (10 OE)

Front 12

When to mask speech audiometry:

How much masking speech:

Where:

Back 12

presentation level(test ear) - IA> best BC(NTE)

mid masking level = (max masking level + min masking level) / 2

min masking level = presentation level(test ear) - IA + max AB Gap(NTE)

Front 13

List and describe one speech audiometry test material/word list/protocol for children and one for adults for both threshold and supra-threshold testing.

Back 13

- Threshold (kids) - PAL PB 50 Words

- selected words that also appeared in the international kindergarten vocabulary list

- Suprathreshold (kids) - WIPI (Words intelligibility picture identification)

- closed set test with either picture pointing or receptive vocabulary

- Threshold (adults) - SRT using spondee words

- testing each ear and gaining thresholds in response to these multisyllabic words

- Suprathreshold (adult) - W-22 or NU-6

- obtaining percentage scores of words correct at a starting level of either the patient’s MCL or 30-40 dB above their pure tone thresholds

Front 14

Site of lesion testing is one use of speech audiometry, list and describe two other uses.

Back 14

- Applications in hearing aid fitting/rehab - It is important to know what areas a patient will hear and understand. Speech is the way they have access to the entire spectrum of speech sounds within their hearing loss. It is also important to know how a patient will hear and understand within background noise so doing speech in noise testing is also important to this concept.

- Can provide validation of rehab intervention - when recommending hearing aids to a candidate, there is emotion involved. Providing test results validates their concerned with how they understand speech, but also stresses the importance of amplification.

Front 15

When and how would you use the information from the Thornton & Raffin / SPRINT / Carney & Schlaugh data?; if someone asked you why you were using this data, tell me how you would defend your position.

Back 15

- Thornton and Raffin - Bionomial distribution model; They investigated the critical differences between one score and a retest score that would be necessary for those scores to be considered statistically significant. Their findings showed that with an increasing set size, variability decreased. It would seem that more items are better.

- SPRINT chart is more user friendly than the Thornton and Raffin. 2 data sets contained within it.

- Carney and Schlaugh took the old Thornton and Raffin data and re-analyzed it, they had different analytical ways of looking at the data.

- The purpose of knowing this data is to determine whether or not the person is experiencing something retrocochlear or to determine phonemic regression. You can bring someone in and gather a range of data from their word recognition scores. The research shows that we can use this data to determine differences in word recognition and we can see if anyone is unusually low.