SHS 221 Module 6C

• Continuous pure tones

• Pulsed tones

• Frequency-modulated tones

What types of pure-tone stimuli are used in hearing assessment?

A tone presented continuously for a period of time

What is a continuous pure tone?

A tone presented in brief, repeated bursts rather than continuously

What is a pulsed tone?

Frequency-modulated tone

A tone whose frequency varies by approximately ±5% of its center frequency

To avoid standing waves

Why are frequency-modulated tones used in sound-field testing?

It activates a narrow region on the basilar membrane

What does it mean for a tone to be frequency-specific?

Broadband noise and narrowband noise

What are the two types of noise used in hearing assessment?

Broadband noise

Noise that can contain all tones, or an effectively infinite number of tones. Its bandwidth depends on the transducer

Narrowband noise

Frequency-specific noise

Intensity

The physical magnitude of sound

Loudness

What is the perceptual equivalent of intensity?

Decibels Hearing Level. The 0 dB HL reference represents average human hearing threshold at a given frequency

What does dB HL stand for, and what is its referece?

Sound pressure level, with a reference of 20 µPa

What does dB SPL measure?

dB SPL measures actual sound pressure, while dB HL is normalized to typical human hearing sensitivity at different frequencies

What is the difference between dB SPL and dB HL?

Cycles per second, or Hertz (Hz)

What is frequency measured in?

Pitch

What is the perceptual equivalent of frequency?

Octave frequency

A frequency that is double or half another frequency

Octave frequencies

250, 500, 1000, 2000 Hz is an example of what?

A sound level corresponding to the average hearing threshold of a statistically normal young adult at that frequency. It does not mean silence.

What does 0 dB HL mean?

Mid-frequencies, approximately 1,000-4,000 Hz

At which frequencies is the human ear most sensitive?

Low frequencies below 500 Hz

At which frequencies does the human ear have poorer sensitivity?

Why the dB HL scale is preferred in clinical audiology

It is normalized to human hearing, accounts for frequency-specific sensitivity, allows comparison to normal hearing, provides a universal clinical language, standardizes audiogram plotting, and is easy to interpret

Audiogram

A graph used to plot hearing thresholds in dB HL as a function of test frequencies

The amount of hearing loss is related to the threshold value in dB HL

What does the threshold value on an audiogram indicate?

Sloping, flat, notch, and cookie-bite

What are four common audiogram patterns?

Why an audiogram is useful

Helps identify hearing patterns, classify hearing loss severity, monitor changes over time, and share results among professionals

Octave frequencies are spaced by doubling frequencies; inter-octave frequencies fall between octave frequencies

What are octave frequencies compared with inter-octave frequencies?

1,000, 2,000, 3,000, 4,000, 6,000, and 8,000 Hz, then retest 1,000 Hz, followed by 500 and 250 Hz

What is the air conduction test frequency order under ASHA (2005)?

When the 500 Hz and 1,000 Hz thresholds are greater than 20 dB HL

When is 750 Hz tested?

Right ear: red. Left ear: blue

What colors represent each ear’s threshold on an audiogram?

1,000, 2,000, 3,000, and 4,000 Hz, then retest 1,000 Hz, followed by 500 and 250 Hz.

What is the bone conduction test frequency order?

Approximately 1-2 seconds

How long should a continuous tone be presented?

Benefits of pulsed tones

They reduce the number of presentations needed to find a threshold, help distinguish test tones from continuous tinnitus, and reduce false-positive responses

The Modified Hughson-Westlake Procedure

What procedure is used to measure pure-tone hearing thresholds?

Familiarization

Introducing the patient to the test tone before beginning the threshold search

A 1,000 Hz tone presented for 1–2 seconds at a comfortable level, such as 30–40 dB HL.

What tone is used for familiarization, and at what level?

The threshold search begins

What happens if the patient hears the familiarization tone?

Increase the level to 50 dB HL, then increase it in 10 dB steps until the patient responds.

What happens if the patient does not hear the familiarization tone?

Decrease the tone by 10 dB after a heard response and increase it by 5 dB after a response indicating the tone was not heard

What is the Hughson-Westlake 10 dB down, 5 dB up procedure?

Decrease the intensity by 10 dB

What do you do if the patient hears the tone?

Increase the intensity by 5 dB

What do you do if the patient does not hear the tone?

When the patient responds at least 50% of the time at a given level, with two out of three “yes” responses during the ascending direction.

When is a threshold considered established?

Air conduction thresholds are ear-specific. Bone conduction thresholds are not truly ear-specific without masking

Are ear-specific thresholds obtained during air conduction and bone conduction testing?

If both are below 15 dB HL, cochlear responses are considered similar, and bone conduction thresholds are obtained from the better ear with lower thresholds

What happens when air conduction thresholds in both ears are within normal limits?