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M. Yüksel et al.
The sound pressure level is typically assessed using sound level meters equipped
with integrated software and averaging capabilities. A standard sound level meter
comprises a high-quality microphone, a preamplier, and an analog-to-digital converter to transform the analog electrical signal into a digital format, a processor for
necessary calculations, and a display screen to present the results. In an audiology
laboratory, the tone levels rely on a specic calibration, since the sound pressure
level generated by the acoustic transduction system on the patient’s ear needs to be
taken into account in a standardized way.
7.3 Psychoacoustics
There are several important concepts in psychoacoustics that may be of interest to
otology and audiology professionals. In the context of this section, we focus on
loudness, auditory masking, and binaural hearing.
7.3.1 Loudness
Loudness, representing how loud sounds are perceived, holds fundamental importance in otology and audiology. It plays a crucial role in restoring hearing sensitivity
and perception, guiding the selection and programming of hearing assistive devices.
The sensation of loudness is inuenced by both listener-specic and stimulusrelated factors. Parameters such as intensity, spectral composition, duration, and
context of the stimulus interact with the listener’s auditory sensitivity and hearing
loss. Loudness encompasses the frequency-specic, nonlinear, and temporal aspects
related to sound intensity perception. For instance, a 60dB SPL tone at frequencies
of 0.25 and 1kHz will not be perceived as equally loud. The unequal sensitivity of
the human ear to various frequencies is, on one hand, a consequence of anatomical
features. Uneven sensitivity begins with the auricle and external auditory canal,
which amplify and shape sound for frequencies above 1000Hz [3]. On the other
hand, the “critical bands” within the cochlea affect how the sound’s intensity is
integrated over frequency, making them important for nearly every aspect of
psychoacoustics.
7.3.1.1 Critical Bands andLoudness
Critical bands stem from the vibrational pattern of the basilar membrane: a tone will
evoke a vibration pattern with a certain width and shape that peaks at a location
7 Acoustics, Psychoacoustics, andProperties ofSound
119
specic to its frequency. The effective bandwidth directly affects loudness, frequency resolution, and auditory masking since the bandwidth reects the hearing
systems’ resolving ability for simultaneous stimuli.
As suggested and later demonstrated by the seminal works of Eberhard Zwicker
and Donald D.Greenwood [4–6], critical bands represent equal distances on the
basilar membrane, with each band covering an area of approximately 1.3 mm.
Zwicker proposed a constant bandwidth of 100 Hz up to a center frequency of
500 Hz and roughly a relative bandwidth of 20% for center frequencies above
500Hz, i.e., an exponential increase if expressed in hertz [7]. Therefore, at a center
frequency of 2150Hz, the bandwidth is roughly 320Hz, corresponding roughly to
a 1.3-mm extension along the basilar membrane. Similarly, at the center frequency
of 8500Hz, the bandwidth is 1800 Hz, also corresponding roughly to a 1.3-mm
distance along the basilar membrane.
Loudness perception is associated with the number and rate of neural spikes
transmitted to the central auditory system, but loudness is affected by critical bands.
When a listener compares the combined loudness of two simultaneously presented
tones with a reference tone, their combined loudness increases when the tones are
separated by more than a critical bandwidth. In fact, loudness about doubles for
larger separations, indicating that the loudness produced by each tone adds up.
Their combined loudness is smaller when the frequency separation is smaller than
the critical bandwidth, since both tones interact in the same critical band.
Equal loudness contours, which represent how audio signals at different frequencies are perceived as having the same loudness level, were rst measured monaurally by Kingsbury [8] and later binaurally by Fletcher and Munson [9]. These
contours have been rened over the years in various standardization efforts to provide a more accurate understanding of loudness perception across frequencies [10].
7.3.1.2 Measurement: Phons andSones
Using the same procedure as for measuring equal loudness contours, one can nd
the sound pressure level of a pure tone of 1000Hz that is as loud as a sound in question. This equally loud 1-kHz tone thus expresses the loudness of an arbitrary sound.
Its SPL is dened as the “loudness level” expressed in phons. For example, a sound
with 30 phon evokes the same loudness as a 1-kHz tone presented at 30dB SPL.
On the other hand, the sone is a unit of loudness that scales with perceived loudness, meaning that doubling the number of sones corresponds to a doubling of perceived loudness. Therefore, if a sound is judged by a listener to be n times louder
than a 1-sone tone, its loudness is n sones. It is known that to double the sensation
of loudness, the level of a 1-kHz tone needs to be elevated by 10dB for sounds
above 40dB SPL. For instance, to achieve a doubling of loudness, a 40dB SPL
(phon) needs to be increased to a 50dB SPL (phon) and then corresponding to a
perception of two sones. These relationships hold for sounds of at least 200-ms
duration. Additional considerations will reect the temporal evolution of the sound
and binaural integration [4] .
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M. Yüksel et al.
7.3.2 Auditory Masking
Auditory masking expresses the observation that one sound or spectral component
can become inaudible in the presence of another—the “weaker” component is then
masked by the “masker.” Auditory masking can be categorized into simultaneous
and temporal masking based on the time differences between the target and masker.
7.3.2.1 Simultaneous Masking
Simultaneous masking largely depends on the intensity and spectrum of the target
and masker signals. More intense tones naturally mask less intense ones, but this
relationship varies according to the frequency spectrum and the critical bands occupied by the masker and target tones. Fletcher [11] conducted experiments testing the
threshold of a pure tone against varying noise masker bandwidths. The noise was
centered at the frequency of the target tone, with constant noise power density. The
results showed that as the noise bandwidth increased, the threshold for the target
tone also increased. However, once the masker width exceeded the critical band
limit, there was no signicant change in the threshold for the target signal. This
early experiment led to the development of the power spectrum model of masking,
which posits that the threshold of a signal at a given frequency is determined by the
amount of masker energy passing through an auditory lter centered on that
frequency.
Several classical studies conducted through the 1920s–1970s have provided
essential observations about masking [5, 12–14]. The strongest masking occurs near
the masker frequency and masking decreases as the distance from this frequency
increases, masking increases with a higher masker intensity, and the masking effect
is symmetrical around the masker frequency at lower masker levels (20–40dB).
However, as masker intensity increases, the masking pattern widens asymmetrically, with greater masking occurring at frequencies higher than the masker frequency, known as the upward spread of masking. The upward spread of masking
reects the activity along the basilar membrane. The traveling wave gradually
increases in amplitude along the basal (high-frequency) part of the cochlea, peaks,
and then rapidly decays in the apical (low-frequency) part. Consequently, higher
(more basal) frequencies are more affected by the displacement pattern caused by
lower-frequency stimuli.
7.3.2.2 Temporal Masking
Temporal masking is a nonsimultaneous masking in which the audibility of one
sound is affected by a preceding or following sound. Temporal masking may occur
in two ways depending on the sequence of sounds: if the signal is presented rst and
followed by the masker, it is called pre-masking or backward masking; if the masker
is presented rst and followed by the signal, it is called post-masking or forward
masking.
The amount of masking depends on the masker level, duration, spectrum of the
masker and target tones, and the time interval between the masker and the target
signal. Forward masking, where a masker precedes a signal, lasts between 100 and
7 Acoustics, Psychoacoustics, andProperties ofSound
121
200ms for long-duration sounds and decays linearly on a logarithmic scale over
time, regardless of masker intensity. In forward masking, an increase in masker
level typically results in only a minor increase in the signal threshold, provided the
signal level is below approximately 40dB SPL [15].
Temporal masking, whether forward or backward, decreases rapidly as the time
interval between the masker and the target signal increases. Generally, no masking
occurs when the interval exceeds 200ms for forward masking, and the masking
effect is most prominent within intervals of up to 50ms for forward masking and
25ms for backward masking [15–18].
The phenomenon of temporal masking can be attributed to several factors. Moore
[19] summarized ve key contributors: (1) the basilar membrane’s response to the
masker persists after the masker ends, known as “ringing,” and overlaps with the
signal response, thereby contributing to masking, particularly at low frequencies
where the duration of ringing is longer; (2) the masker causes short-term adaptation
in the auditory nerve or higher centers, reducing the response to a signal immediately following the masker; (3) neural activity induced by the masker persists
beyond the auditory nerve, masking the subsequent signal; (4) the masker triggers
inhibition in the central auditory system that lasts beyond the masker’s end, affecting the signal response; (5) the masker activates the efferent system, lowering the
active mechanism’s gain and reducing the signal’s effective level, especially for
maskers lasting more than a few tens of milliseconds, as this duration is required for
efferent system activation.
7.4 Fundamentals ofBinaural Hearing
7.4.1 Temporal Aspects: Envelope andFine Structure ofSound
In a typical functioning cochlea, sounds of a broad frequency range such as speech
and music are separated, or ltered, into signals of narrower frequency bands. Each
of these signals can be viewed as a temporal amplitude envelope, which changes
relatively slowly, superimposed on a carrier signal that oscillates fast (temporal ne
structure—TFS). At the auditory nerve level, the envelope is encoded as uctuations
in the ring rate over a span of several milliseconds. In contrast, the TFS is encoded
as the synchronization of neural ring to the individual cycles of the stimulus waveform [20, 21].
The envelope refers to the slower amplitude variations over time in an acoustic
signal. It is relatively easy to understand a single speaker using only envelope cues,
even with limited frequency bands of as few as ve spectral channels when listening
to a closed set of words [22, 23]. Hence, the temporal envelope (TE) is often considered a good source of information for speech perception in a quiet background.
Besides, prosodically, TE conveys intonation, stress patterns, and emotional content
[24, 25].
The TFS refers to the phase information in the sound signal, providing spectrotemporal detail. In speech perception, the TFS plays a crucial role and contributes
122
M. Yüksel et al.
signicantly to understanding speech in noisy environments [26, 27]. There has
been long-standing controversy regarding the extent to which these two acoustic
properties contribute to the intelligibility of speech. Even though envelope coding is
prominent compared to the TFS for speech perception, the inclusion of TFS cues is
important in order to fully explain the impact of background noise modulations on
the ability of humans to identify speech [28] and the contribution of spatial location
and binaural unmasking [29, 30].
7.4.2 Spatial Hearing
Spatial hearing is a remarkable feature of auditory perception that enables us to
robustly locate the source of a sound in our environment. It plays a crucial role in
auditory scene analysis, allowing us to distinguish between different sound sources
and focus our attention on specic stimuli. For instance, imagine being in a forest.
Spatial hearing allows you to detect the rustle of leaves or the snap of a twig, providing vital information about potential predators or other unseen creatures. This ability also comes into play in complex acoustic environments, such as crowded social
gatherings or bustling city streets. In such scenarios, spatial hearing assists in isolating specic voices or sounds, facilitating selective attention. For instance, when
engaged in a conversation amidst a group of people, spatial cues help us focus on
the speaker while ltering out background noise. Thus, spatial hearing provides
localization cues, improves speech perception in noise, and helps direct attention
[31, 32].
Spatial hearing relies strongly on binaural mechanisms that allow listeners to
utilize interaural time differences (ITDs) and interaural level differences (ILDs), the
variations in the time of arrival and intensity between the sounds at both ears,
respectively [33]. The head creates an acoustic shadow for lateral sound sources,
resulting in an ILD between the shadowed ear and the ear toward the source. The
ILD varies with the angle, frequency, distance, and individual characteristics [34].
The ITD increases monotonically with the lateral angle, reaching a maximum of
approximately 700–800μs [35].
By processing and comparing these brief time differences, and integrating ILD
and spectral cues, the brain creates a composite representation of the sound’s location, with the weighting of these cues depending on the stimulus and listening context [36–38]. Low-frequency ITDs are primarily transmitted through phase-locked
neural ring to the TFS.At high frequencies, phase locking is not maintained, so
ITDs are conveyed only through the temporal envelope. Discrimination thresholds
for envelope ITDs tend to be considerably higher than those for ne structure ITDs
[39] and are affected by the shape of the envelope [40–42]. Generally, ITDs from
the temporal ne structure and envelope aid inlocalization, but ILDs may contribute
signicantly or even dominate, if high-frequency components are present in the
sound [36, 37, 43]. When background noise is present, the auditory system will rely
on any cues available [44–46].
7 Acoustics, Psychoacoustics, andProperties ofSound
123
References
1. Everest FA, Pohlmann K.Master handbook of acoustics. 5th ed. NewYork, NY: McGraw Hill
Professional; 2019.
2. Kinsler LE, Frey AR, Coppens AB, Sanders JV.Fundamentals of acoustics. 5th ed. NewYork:
John Wiley & Sons; 2000.
3. Rosowski JJ.The effects of external-and middle-ear ltering on auditory threshold and noiseinduced hearing loss. J Acoust Soc Am. 1991;90(1):124–35.
4. Fastl H, Zwicker E, editors. Psychoacoustics: facts and models. Berlin, New York:
Springer; 2007.
5. Greenwood DD.Auditory masking and the critical band. J Acoust Soc Am. 1961;33(4):484–502.
6. Greenwood DD.Critical bandwidth and the frequency coordinates of the basilar membrane. J
Acoust Soc Am. 1961;33(10):1344–56. https://doi.org/10.1121/1.1908437.
7. Seeber BU.Masking and critical bands. In: Havelock D, Kuwano S, Vorländer M, editors.
Handbook of signal processing in acoustics. Berlin, NewYork: Springer; 2008. p.229–40.
8. Kingsbury B.A direct comparison of the loudness of pure tones. Phys Rev. 1927;29(4):588.
9. Fletcher H, Munson WA. Loudness, its denition, measurement and calculation. Bell Syst
Tech. 1933;12(4):377–430.
10. ISO. 226:2023 Normal equal-loudness-level contours. Acoustics: International Organization
for Standardization; 2023. p.20.
11. Fletcher H.Auditory patterns. Rev Mod Phys. 1940;12(1):47.
12. Wegel R, Lane C.The auditory masking of one pure tone by another and its probable relation
to the dynamics of the inner ear. Phys Rev. 1924;23(2):266.
13. Ehmer RH. Masking patterns of tones. J Acoust Soc Am. 1959;31(8):1115–20. https://doi.
org/10.1121/1.1907836.
14. Small AM Jr. Pure-tone masking. J Acoust Soc Am. 1959;31(12):1619–25.
15. Jesteadt W, Bacon SP, Lehman JR.Forward masking as a function of frequency, masker level,
and signal delay. J Acoust Soc Am. 1982;71(4):950–62. https://doi.org/10.1121/1.387576.
16. Elliott LL. Backward masking: monotic and dichotic conditions. J Acoust Soc Am.
1962;34(8):1108–15. https://doi.org/10.1121/1.1918253.
17. Smiarowski RA, Carhart R.Relations among temporal resolution, forward masking, and simultaneous masking. J Acoust Soc Am. 1975;57(5):1169–74. https://doi.org/10.1121/1.380575.
18. Wilson RH, Carhart R.Forward and backward masking: interactions and additivity. J Acoust
Soc Am. 1971;49(4, Suppl. 2):1254. https://doi.org/10.1121/1.1912488.
19. Moore B. Frequency selectivity, masking, and the critical band. In: Moore BC, editor. An
introduction to the psychology of hearing. 6th ed. Danvers, MA: Brill; 2013. p.112.
20. Johnson DH.The relationship between spike rate and synchrony in responses of auditory-nerve
bers to single tones. J Acoust Soc Am. 1980;68(4):1115–22. https://doi.org/10.1121/1.384982.
21. Joris PX. Interaural time sensitivity dominated by cochlea-induced envelope patterns. J
Neurosci. 2003;23(15):6345–50. https://doi.org/10.1523/jneurosci.23- 15- 06345.2003.
22. Dorman MF, Loizou PC.Speech intelligibility as a function of the number of channels of
stimulation for normal-hearing listeners and patients with cochlear implants. Am J Otol.
1997;18(Suppl. 6):S113–4. https://doi.org/10.1121/1.419603.
23. Shannon RV, Zeng F-G, Kamath V, Wygonski J, Ekelid M.Speech recognition with primarily
temporal cues. Science. 1995;270(5234):303–4. https://doi.org/10.1126/science.270.5234.303.
24. Rosen S. Temporal information in speech: acoustic, auditory and linguistic aspects. Philos
Trans R Soc Lond Ser B Biol Sci. 1992;336(1278):367–73.
25. Sharpe V, Fogerty D, den Ouden D-B. The role of fundamental frequency and temporal envelope in processing sentences with temporary syntactic ambiguities. Lang Speech.
2017;60(3):399–426.
26. Gnansia D, Péan V, Meyer B, Lorenzi C.Effects of spectral smearing and temporal ne structure degradation on speech masking release. J Acoust Soc Am. 2009;125(6):4023–33.
124
27. Hopkins K, Moore BC. The contribution of temporal ne structure to the intelligibility of
speech in steady and modulated noise. J Acoust Soc Am. 2009;125(1):442–6. https://doi.
org/10.1121/1.3037233.
28. Moon IJ, Won JH, Park M-H, Ives DT, Nie K, Heinz MG, etal. Optimal combination of neural
temporal envelope and ne structure cues to explain speech identication in background noise.
J Neurosci. 2014;34(36):12145–54.
29. Bischof NF, Aublin PG, Seeber BU.Fast processing models effects of reections on binaural
unmasking. Acta Acustica. 2023;7:11.
30. Seeber BU, Hafter ER.Failure of the precedence effect with a noise-band vocoder. J Acoust
Soc Am. 2011;129(3):1509–21. https://doi.org/10.1121/1.3531836.
31. Avan P, Giraudet F, Büki B.Importance of binaural hearing. Audiol Neurootol. 2015;20(Suppl.
1):3–6. https://doi.org/10.1159/000380741.
32. Rennies J, Kidd G Jr. Benet of binaural listening as revealed by speech intelligibility and
listening effort. J Acoust Soc Am. 2018;144(4):2147–59.
33. Rayleigh LXII.On our perception of sound direction. London Edinburgh Philos Mag J Sci.
1907;13(74):214–32.
34. Seeber BU, Fastl H.Localization cues with bilateral cochlear implants. J Acoust Soc Am.
2008;123(2):1030–42.
35. Cai T, Rakerd B, Hartmann WM. Computing interaural differences through nite element
modeling of idealized human heads. J Acoust Soc Am. 2015;138(3):1549–60.
36. Seeber B. The duplex-theory of localization investigated under natural conditions. In:
Proceedings of the ICA 2007, 19th International Congress on Acoustics, Madrid, Spain, 2–709
2007; 2007.
37. Wiggins IM, Seeber BU.Dynamic-range compression affects the lateral position of sounds. J
Acoust Soc Am. 2011;130(6):3939–53.
38. Wiggins IM, Seeber BU.Effects of dynamic-range compression on the spatial attributes of
sounds in normal-hearing listeners. Ear Hear. 2012;33(3):399–410.
39. Nuetzel JM, Hafter ER.Discrimination of interaural delays in complex waveforms: spectral
effects. J Acoust Soc Am. 1981;69(4):1112–8.
40. Bernstein LR, Trahiotis C. How sensitivity to ongoing interaural temporal disparities is
affected by manipulations of temporal features of the envelopes of high-frequency stimuli. J
Acoust Soc Am. 2009;125(5):3234–42.
41. Klein-Hennig M, Dietz M, Hohmann V, Ewert SD. The inuence of different segments of the ongoing envelope on sensitivity to interaural time delays. J Acoust Soc Am.
2011;129(6):3856–72.
42. Monaghan JJ, Krumbholz K, Seeber BU.Factors affecting the use of envelope interaural time
differences in reverberation. J Acoust Soc Am. 2013;133(4):2288–300.
43. Macpherson EA, Middlebrooks JC.Listener weighting of cues for lateral angle: the duplex
theory of sound localization revisited. J Acoust Soc Am. 2002;111(5):2219–36.
44. Kerber S, Seeber BU.Sound localization in noise by normal-hearing listeners and cochlear
implant users. Ear Hear. 2012;33(4):445–57.
45. Kerber S, Seeber BU.Localization in reverberation with cochlear implants: predicting performance from basic psychophysical measures. J Assoc Res Otolaryngol. 2013;14:379–92.
46. Lorenzi C, Gatehouse S, Lever C.Sound localization in noise in normal-hearing listeners. J
Acoust Soc Am. 1999;105(3):1810–20.
M. Yüksel et al.
Behavioral andElectrophysiological
Tests inAudiology
EbruKösemihal, ÖmerFarukSüloğlu, MohamadAlfarghal,
andSuzanneC.Purdy
8.1 Introduction
This section discusses the behavioral and electrophysiological tests in audiology.
The evaluation of hearing may require different tests at different ages. In explaining the topics, separate information has been provided by considering children,
adults, and special populations that require detailed evaluation regardless of age.
This provides an understanding of the objective and subjective tests used to assess
the types and degrees of hearing loss and auditory processing disorders.
Information is provided on how to conduct the diagnostic audiology test battery,
which tests provide information about which specic part or function of the auditory
pathway, and how they complement each other. The pure-tone and speech audiometry tests included in the audiological test battery provide valuable information about
an individual’s behavioral response to sound and speech stimuli. The objective measures include acoustic immittance audiometry, otoacoustic emissions (OAEs), and
auditory evoked potential (AEP) responses. Objective assessments provide better
information for evaluating the anatomical and physiological functioning of the
8
E. Kösemihal (*)
Near East University, Faculty of Health Scienses, Department of Audiology, Nicosia, Cyprus
e-mail: ebru.kosemihal@neu.edu.tr
Ö. F. Süloğlu
Istanbul Medeniyet University, Faculty of Health Sciences, Department of Audiology,
Istanbul, Turkey
e-mail: omer.suloglu@medeniyet.edu.tr
M. Alfarghal
King Abdulaziz Medical City, Hearing, and Balance Clinic, Jeddah, Saudi Arabia
S. C. Purdy
University of Auckland, School of Psychology, Discipline of Speech Science,
Auckland, New Zealand
e-mail: sc.purdy@auckland.ac.nz
© The Author(s), under exclusive license to Springer Nature
Switzerland AG 2024
M. T. Kalcioglu et al. (eds.), Otology Updates, Comprehensive ENT,
https://doi.org/10.1007/978-3-031-76173-7_8
125
126
auditory system. For this reason, they should be included in the test battery. This section describes how to perform these tests and how to interpret the results.
E. Kösemihal et al.
8.2 Case History
Audiologists review and interpret history and combine it with anatomical and
physiological and audiometric information to make the appropriate diagnosis.
Filling out an interview form while taking history helps organize and record the
information obtained. In addition to asking about the main complaint, questions
may be asked about the patient’s history of hearing problems, their family history
of hearing or speech/language problems, hereditary hearing loss, and existing medical conditions (thyroid, diabetes, multiple sclerosis, etc.). Working in a noisy environment, ear discharge or pain, sudden, uctuating, or unilateral hearing loss,
tinnitus, and dizziness are conditions and symptoms that help in the diagnosis.
Information about the impact of hearing difculties (e.g., difculties hearing group
conversations in the family or at work) can also indicate the likely degree and conguration of hearing loss. Each clinic can create its own case history form. In addition, there may be a section for the clinician’s comments and thoughts. Besides
noting the degree, type, and conguration of hearing loss, the audiologist may also
add what pathology the ndings are “compatible (or consistent) with.” In this way,
the information obtained from the patient can be combined with the data obtained
and included in the report [1].
8.3 The Audiology Test Room
Since it will be difcult to reduce sounds such as crowded corridors, trafc noise,
and mechanical equipment, the quiet room should be located as far away from
these as possible. Installation of sound-absorbing doors, windows, and quiet ventilation systems is also essential. Therefore, it is advisable to consider the use of
acoustical doors, glazing, and attenuating airways in the early stages of room
design and location.
The test room in which the audiometric assessment is performed should be at
least 8m2. For pediatric or free-eld evaluations, the width of the test room can be
increased to 24m2 if appropriate. The size of the room also reduces acoustic problems such as echoes from furniture, equipment, and people [2]. An appropriately
sized and sound-treated room ensures adequate acoustical testing conditions as well
as accommodating family members supporting the person being assessed.
Single or double walls may be installed in the test room, depending on the desired
level of acoustic insulation. A single wall typically provides 40–45dB of attenuation,
while a double wall can provide 70–75dB.Insulation materials such as Styrofoam,
glass wool, and rock wool can be used in the test room. Reverberation times should
be <0.25s in a soundproof test room. Absorption is used on the walls and ceiling of
the room. In newly constructed buildings, absorptive surfaces can be used to construct walls. The American National Standards Institute (ANSI) and the International
8 Behavioral andElectrophysiological Tests inAudiology
127
Organization for Standardization (ISO) provide guidelines for ambient sound pressure levels (SPLs) during testing, specifying frequencies and levels [2]. These criteria can be found in ANSI 53.1–1999 and ISO 8253-1:2010, part 11 [3].
If the patient’s seating position is similar to that of the audiologist, the patient
can take cues from the audiologist’s facial expressions and movements. For this
reason, patients should be seated sideways. For free-eld testing, loudspeakers
should be placed at head height and 1 meter from the patient. Patient position and
loudspeaker angle may vary depending on the tests being performed. Care should
be taken to minimize unnecessary furniture and reective surfaces in the test room,
which can impact the required uniform radiation pattern from the loudspeaker
required for free-eld testing. Acoustic rooms are enclosed, making it difcult to
control fresh air and temperature. Therefore, a full acoustically designed air-conditioning system should provide adjustable temperature and humidity control within
the room.
8.4 Behavioral Evaluation ofHearing
8.4.1 Pure-Tone Audiometry
A pure-tone audiometry test is used to determine the hearing thresholds for each ear.
This test is performed in a quiet environment. An audiometer and transducers (headphones, insert earphones, and bone vibrators) are used to perform a pure-tone audiometry test [3, 4]. Calibration of each transducer of the audiometer is essential
because their physical properties and placement patterns can cause the sound they
produce to vary. The calibration date should be displayed on the audiometer, and
transducers should not be switched between instruments. Transducer output is measured in sound pressure level (SPL). However, because hearing tests use decibel
hearing level (dB HL) values for audiometric thresholds, SPL values must be converted into dB HL [3–6]. The audiometer transmits signals to the patient via a transducer. These signals include pure-tone, speech, or noise stimuli.
Pure-tone audiometry is a conventional test used to assess hearing thresholds and
classify hearing loss [5, 6]. Hearing thresholds are determined by presenting a series
of pure tones ranging from low to high frequencies and by carefully observing the
patient’s response. The audiometric threshold is the lowest level of intensity detected
by the patient in decibels on the hearing level scale (dB HL). In the audiometry test,
the average level of normal hearing is dened by an audiometric 0dB HL.Normal
hearing thresholds range in classication by researchers and professional standards
but are commonly dened as ranging from −10 to 25dB HL [7, 8].
The standard octave frequencies used in audiometric testing are 125, 250, 500,
1000, 2000, 4000, and 8000Hz. The pure-tone test frequency order is specied in
audiometry standards as 1000, 2000, 4000, 8000, and then 500 and 250Hz. The
lowest audiometric frequency, 125Hz, is typically only tested when there is a severe
to profound hearing loss, in an effort to identify any residual hearing. If there is a
difference of 20dB or more between two octave frequencies, hearing thresholds are
also obtained at intermediate frequencies (750, 1500, 3000, and 6000 Hz). The