This document provides an overview of acoustics and basic audiometry concepts. It defines key terms like frequency, intensity, pitch and loudness. It explains that frequency is a physical property of sound measured in Hertz, while pitch is the human perception of how high or low a sound is. Intensity is the physical measurement of sound pressure in decibels, while loudness is the human perception of sound intensity. The document also reviews concepts like pure tones, complex sounds, fundamental frequency, harmonics, and resonant frequency. It describes how to perform a basic audiologic assessment, including taking a case history, performing puretone audiometry to test air and bone conduction thresholds, and assessing speech recognition.

1. A Review of the Basics:
Acoustics and Basic Audiometry
HIS 230: Advanced Audiometry

2. What is sound?
 In the physical sense
◦ it is a disturbance of molecules that is
propagated through some elastic medium,
like the air
 In the psychological sense
◦ sound is the act of hearing something

3. Simple Harmonic Motion
 The most basic form of sound
 Represented by a sine wave, a series
of repeated compressions and
rarefactions
Valente, page 8

4. Acoustics vs.
Psychoacoustics
 Acoustics are physical properties of a
sound that can be measured
◦ Frequency, intensity, wavelength
 Psychoacoustics refers to our
human perceptions of sound
◦ pitch and loudness

5. Frequency
 The number of cycles per second
◦ One cycle consists of one compression and
one rarefaction of the molecules in the medium
(air)
 Unit of measure=Hertz (Hz)
◦ Human ear bandwidth=20 to 20,000 Hz
 1000 Hertz = 1 kiloHertz (kHz)

6. Pure Tone vs. Complex
Sound
 A pure tone has almost all its energy
located at one frequency (sine wave)
◦ We use pure tones during audiometric
testing
 A complex sound is composed of
multiple frequencies
◦ Most of the sounds in our day-to-day lives
are complex in nature
 speech

7. Frequency and Pitch
 Recall that frequency is an acoustic
property of sound that can be
physically measured
◦ Unit of measure is the hertz (Hz)
 Pitch is a psychoacoustic property of
sound, in that it represents our human
perception of how “high” or “low”
sounds of various frequencies are.

8. Frequency & Wavelength
 Wavelength=the distance
a soundwave travels
during one cycle of
vibration
◦ Low frequency sounds have
a longer wavelength
◦ High frequency sounds
have a shorter wavelength
 If the waves at left
occurred over 1 second,
what would the frequency
of each be?
◦ 3 Hz
Image from:
blog.leeburrows.com

9. Fundamental Frequency
 The fundamental
frequency is the
frequency in a
complex sound that
has the lowest
frequency and the
most energy (100 Hz)
 Harmonics are
multiples of the
fundamental frequency
and contain less
energy than the
fundamental frequency
or the preceding
harmonic (300, 500,
700, 900 Hz)
Image from: beausievers.com

10. Resonant Frequency
 The resonant frequency is the frequency at
which a system will be most easily set into
vibration
◦ It is the point where mass and stiffness are equal and
there is no opposition to the flow of energy
 In a tube, with one open end and one closed end:
◦ The longer the tube, the lower the resonant frequency
◦ The shorter the tube, the higher the resonant
frequency
 The average resonant frequency of the ear canal
is approximately 3000 Hz, but will vary depending
on the patient’s ear canal size and shape!
 Note: this will be very important in the fitting of
hearing aids and is the reason why individual
REAL-EAR VERIFICATION is so important

11. Intensity and Loudness
 Recall that intensity is an acoustic
property of sound that can be
physically measured
◦ Unit of measure is the decibel (dB)
 Loudness is a psychoacoustic
property of sound, in that it represents
our human perception of how “loud” or
“soft” sounds of various intensities are.

12. Intensity
 Unit of measure=decibel (dB)
◦ Human ear dynamic range=0-140 dB SPL
 dB scale is a logarithmic scale
◦ This allows for the huge range of sound pressures that
our ears can detect to be stated in simpler terms
 Several dB scales exist, each with a different
frame of reference. We are most interested in
the following:
◦ dB SPL (sound pressure level)
◦ dB HL (hearing level)
◦ dB SL (sensation level)

13. dB SPL
 SPL=sound pressure level
◦ A pressure measurement
 Commonly used to express noise
measurements with a sound level meter
 The most common dB scale used in hearing
aid testing (electroacoustic/test box and real-
ear measurements)

14. dB HL
 HL=hearing level; the dB level on the
audiometer when performing a hearing test.
 Ours ears do NOT have a flat frequency
response
◦ They are more sensitive in the mid-frequencies
(500-5000 Hz) than at other frequencies
 the average normal hearing person has a threshold of 7
dBSPL at 1000 Hz, but it requires almost 50 dBSPL to
hear a sound at 125 Hz.
 Each of these levels for normal hearing in dB SPL is
equal to 0 dB HL (audiometric zero).
 Without dB HL, a normal audiogram would
form an arched shape rather than a straight
line, which would be difficult to explain to
patients!

15. dB SL
 SL=sensation level; the amount of dB
over a patient’s threshold
◦ Commonly used to refer to the level by
which one should perform speech testing
◦ Also used in the assessment of tinnitus
and tinnitus masking

16. AUDIOLOGIC
ASSESSMENT

17. You can’t fit a hearing aid until you
can perform/interpret an audiogram!
 Being able to perform an accurate
hearing test and interpret the obtained
results are imperative to:
◦ Making appropriate recommendations
 Is a medical referral required?
 Amplification options
 Hearing aids versus cochlear implant?
◦ Fitting hearing aids appropriately!

18. Before the audiogram…
 The test environment should meet ANSI
standards:
◦ Calibrated equipment
 The calibration of testing equipment is generally
required annually by each state as part of
professional licensure.
 Each audiometer is calibrated with its specific
headphones/inserts coupled to it and in the test
booth that it corresponds to. You cannot move
headphones or audiometers around at will.
 Daily listening checks are important (See Table 3-3)
◦ Preferably, a sound isolation booth
 To reduce the likelihood of artifacts created by other
noises in the environment

19. Taking a Case History
 Any case history form must provide
space for a statement of the perceived
problem—including why professional
services are being sought.
◦ It is helpful to know the patient/client’s
own attitude about the appointment.
◦ Knowing the reason for the visit can
provide powerful insights before the rest
of the history has been completed or the
first test has been administered.

20. Information to be collected should include:
 Hearing loss query (one or both ears, duration
 Family history of ear disease
 Family history of hearing impairment
 History of noise exposure
 History of head or ear trauma
 Past related ear surgery, childhood
illness/disease
 Reports of vertigo and/or tinnitus
 History of hearing instrument use
Taking a Case History

21. Before the audiogram…
 Seating the patient at a right angle to
the tester allows for the observation of
facial expressions and ease of
communication, without allowing the
patient to watch the tester working,
turning dials, etc.
 Otoscopy should always occur before
your testing begins
 Clear and concise instructions to the
patient help to avoid errors in your
testing

22. Basic Hearing Evaluation
 Audiogram
◦ Puretone audiometry
 Air-conduction (AC) and bone-conduction (BC) testing
◦ Speech audiometry
 Speech reception threshold (SRT)
 This may also be called speech recognition threshold
 Word recognition score (WRS)
 This may also be called speech discrimination score
◦ The goal is to determine
 How well you hear
 How clearly you hear speech
 If there is a medical reason for hearing loss
 If there is a need for some sort of intervention

23. Puretone Audiometry
 Recall that human ears have an audible
bandwidth (frequency range) of 20 to
20,000 Hz
 In audiometric testing, the stimuli are
puretones from 250 to 8000 Hz.
◦ Why?
 because human speech falls within these
frequencies
◦ Most commonly octave bands at 250, 500,
1000, 2000, 4000, and 8000 Hz are tested
◦ The interoctave frequencies of 3000 and
6000 Hz are also commonly tested in adults

24. Puretone Audiometry
 Air-conduction testing
◦ Performed with headphones or insert
earphones
◦ Takes into account the entire auditory
pathway
 Outer ear, middle ear, inner ear, nerve, brain
 Bone-conduction testing
◦ Performed with a bone-conduction oscillator
placed on either mastoid bone (most
common) or the forehead
◦ Directly stimulates the inner ear and nerve
 Bypasses the outer and middle ear

25. Puretone Audiometry
 Threshold is the softest sound that a listener can
hear 50% of the time
 A bracketing technique is used to establish
threshold.
◦ Remember…down 10, up 5.
◦ If the patient responds, reduce the stimulus intensity
by 10 dB. If no response, increase intensity using 5
dB steps. Repeat this procedure until you find
threshold.
 The patient’s thresholds are recorded on the
audiogram.
◦ I prefer to start testing at 1000 Hz at 50 dB HL.
◦ I always use a pulsed puretone, as it is preferred for
patient’s with tinnitus. In addition, it is important to
vary the timing of your presentation of the tones so
the patient isn’t guessing at a pattern

26. Puretone Threshold Symbols
Note: Bone conduction thresholds obtained on the forehead are
indicated by a ^ symbol.

27. Normal Hearing
 Normal AC and BC
thresholds
 Many different
scales exist
regarding degree
of HL
 For the purposes of
this class, we will
use the scale on
the next slide.

28. Degree of Hearing Loss
 This is the exact scale
that I use in interpreting
audiograms
◦ Some clinics are more
liberal and consider
normal hearing to be any
threshold up to 25 dBHL
 In determining the
degree of loss, the
textbook approach
would be to calculate the
puretone average
(PTA=average dB of AC
thresholds at .5, 1, 2
kHz) and compare the
PTA to the scale at right.
From: Northern, J. Hearing Disorders (3rd ed)