Scientific study of sound perception and audiology
Psychoacoustics
is the branch of
psychophysics
involving the scientific study of
sound
perception
and
audiology
?how the human
auditory system
perceives various sounds. More specifically, it is the branch of science studying the
psychological
responses associated with sound (including
noise
,
speech
, and
music
). Psychoacoustics is an interdisciplinary field including psychology,
acoustics
, electronic engineering, physics, biology, physiology, and computer science.
[1]
Background
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Hearing is not a purely mechanical phenomenon of
wave propagation
, but is also a sensory and perceptual event; in other words, when a person hears something, that something arrives at the
ear
as a mechanical sound wave traveling through the air, but within the ear it is transformed into neural
action potentials
. The outer hair cells (OHC) of a mammalian
cochlea
give rise to enhanced sensitivity and better
[
clarification needed
]
frequency resolution of the mechanical response of the cochlear partition. These nerve pulses then travel to the brain where they are perceived. Hence, in many problems in acoustics, such as for
audio processing
, it is advantageous to take into account not just the mechanics of the environment, but also the fact that both the ear and the brain are involved in a person's listening experience.
[
clarification needed
]
[
citation needed
]
The
inner ear
, for example, does significant
signal processing
in converting sound
waveforms
into neural stimuli, so certain differences between waveforms may be imperceptible.
[2]
Data compression
techniques, such as
MP3
, make use of this fact.
[3]
In addition, the ear has a nonlinear response to sounds of different intensity levels; this nonlinear response is called
loudness
.
Telephone networks
and audio
noise reduction
systems make use of this fact by nonlinearly compressing data samples before transmission and then expanding them for playback.
[4]
Another effect of the ear's nonlinear response is that sounds that are close in frequency produce phantom beat notes, or
intermodulation
distortion products.
[5]
The term
psychoacoustics
also arises in discussions about cognitive psychology and the effects that personal expectations, prejudices, and predispositions may have on listeners' relative evaluations and comparisons of sonic aesthetics and acuity and on listeners' varying determinations about the relative qualities of various musical instruments and performers. The expression that one "hears what one wants (or expects) to hear" may pertain in such discussions.
[
citation needed
]
Limits of perception
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]
The human ear can nominally hear sounds in the range
20
Hz
(0.02 kHz)
to
20,000 Hz
(20 kHz).
The upper limit tends to decrease with age; most adults are unable to hear above 16 kHz. The lowest frequency that has been identified as a musical tone is 12 Hz under ideal laboratory conditions.
[6]
Tones between 4 and 16 Hz can be perceived via the body's
sense of touch
.
Human perception of audio signal time separation has been measured to be less than 10 microseconds. This does not mean that frequencies above
100 kHz
are audible, but that time discrimination is not directly coupled with frequency range.
[7]
[8]
Frequency resolution of the ear is about 3.6 Hz within the octave of
1000?2000 Hz.
That is, changes in pitch larger than 3.6 Hz can be perceived in a clinical setting.
[6]
However, even smaller pitch differences can be perceived through other means. For example, the interference of two pitches can often be heard as a repetitive variation in the volume of the tone. This amplitude modulation occurs with a frequency equal to the difference in frequencies of the two tones and is known as
beating
.
The
semitone
scale used in Western musical notation is not a linear frequency scale but
logarithmic
. Other scales have been derived directly from experiments on human hearing perception, such as the
mel scale
and
Bark scale
(these are used in studying perception, but not usually in musical composition), and these are approximately logarithmic in frequency at the high-frequency end, but nearly linear at the low-frequency end.
The intensity range of audible sounds is enormous. Human eardrums are sensitive to variations in the sound pressure and can detect pressure changes from as small as a few
micropascals
(μPa) to greater than
100
kPa
.
For this reason,
sound pressure level
is also measured logarithmically, with all pressures referenced to
20
μPa
(or 1.97385×10
?10
atm
). The lower limit of audibility is therefore defined as
0
dB
,
but the upper limit is not as clearly defined. The upper limit is more a question of the limit where the ear will be physically harmed or with the potential to cause
noise-induced hearing loss
.
A more rigorous exploration of the lower limits of audibility determines that the minimum threshold at which a sound can be heard is frequency dependent. By measuring this minimum intensity for testing tones of various frequencies, a frequency-dependent
absolute threshold of hearing
(ATH) curve may be derived. Typically, the ear shows a peak of sensitivity (i.e., its lowest ATH) between
1?5 kHz,
though the threshold changes with age, with older ears showing decreased sensitivity above 2 kHz.
[9]
The ATH is the lowest of the
equal-loudness contours
. Equal-loudness contours indicate the sound pressure level (dB SPL), over the range of audible frequencies, that are perceived as being of equal loudness. Equal-loudness contours were first measured by Fletcher and Munson at
Bell Labs
in 1933 using pure tones reproduced via headphones, and the data they collected are called
Fletcher?Munson curves
. Because subjective loudness was difficult to measure, the Fletcher?Munson curves were averaged over many subjects.
Robinson and Dadson refined the process in 1956 to obtain a new set of equal-loudness curves for a frontal sound source measured in an
anechoic chamber
. The Robinson-Dadson curves were standardized as
ISO
226 in 1986. In 2003,
ISO 226
was revised as
equal-loudness contour
using data collected from 12 international studies.
Sound localization
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Sound localization
is the process of determining the location of a sound source. The brain utilizes subtle differences in loudness, tone and timing between the two ears to allow us to localize sound sources.
[10]
Localization can be described in terms of three-dimensional position: the
azimuth
or horizontal angle, the
zenith
or vertical angle, and the distance (for static sounds) or velocity (for moving sounds).
[11]
Humans, as most
four-legged animals
, are adept at detecting direction in the horizontal, but less so in the vertical directions due to the ears being placed symmetrically. Some species of
owls
have their ears placed asymmetrically and can detect sound in all three planes, an adaption to hunt small mammals in the dark.
[12]
Masking effects
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Suppose a listener can hear a given acoustical signal under silent conditions. When a signal is playing while another sound is being played (a masker), the signal has to be stronger for the listener to hear it. The masker does not need to have the frequency components of the original signal for masking to happen. A masked signal can be heard even though it is weaker than the masker. Masking happens when a signal and a masker are played together?for instance, when one person whispers while another person shouts?and the listener doesn't hear the weaker signal as it has been masked by the louder masker. Masking can also happen to a signal before a masker starts or after a masker stops. For example, a single sudden loud clap sound can make sounds inaudible that immediately precede or follow. The effects of
backward masking
is weaker than forward masking. The masking effect has been widely studied in psychoacoustical research. One can change the level of the masker and measure the threshold, then create a diagram of a psychophysical tuning curve that will reveal similar features. Masking effects are also used in lossy audio encoding, such as
MP3
.
Missing fundamental
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]
When presented with a
harmonic series
of frequencies in the relationship 2
f
, 3
f
, 4
f
, 5
f
, etc. (where
f
is a specific frequency), humans tend to perceive that the pitch is
f
. An audible example can be found on YouTube.
[13]
Software
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]
The psychoacoustic model provides for high quality
lossy signal compression
by describing which parts of a given digital audio signal can be removed (or aggressively compressed) safely?that is, without significant losses in the (consciously) perceived quality of the sound.
It can explain how a sharp clap of the hands might seem painfully loud in a quiet library but is hardly noticeable after a car backfires on a busy, urban street. This provides great benefit to the overall compression ratio, and psychoacoustic analysis routinely leads to compressed music files that are one-tenth to one-twelfth the size of high-quality masters, but with discernibly less proportional quality loss. Such compression is a feature of nearly all modern lossy audio compression formats. Some of these formats include
Dolby Digital
(AC-3),
MP3
,
Opus
,
Ogg Vorbis
,
AAC
,
WMA
,
MPEG-1 Layer II
(used for
digital audio broadcasting
in several countries), and
ATRAC
, the compression used in
MiniDisc
and some
Walkman
models.
Psychoacoustics is based heavily on
human anatomy
, especially the ear's limitations in perceiving sound as outlined previously. To summarize, these limitations are:
A compression algorithm can assign a lower priority to sounds outside the range of human hearing. By carefully shifting bits away from the unimportant components and toward the important ones, the algorithm ensures that the sounds a listener is most likely to perceive are most accurately represented.
Music
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Psychoacoustics includes topics and studies that are relevant to
music psychology
and
music therapy
. Theorists such as
Benjamin Boretz
consider some of the results of psychoacoustics to be meaningful only in a musical context.
[14]
Irv Teibel
's
Environments series
LPs (1969?79) are an early example of commercially available sounds released expressly for enhancing psychological abilities.
[15]
Applied psychoacoustics
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Psychoacoustics has long enjoyed a symbiotic relationship with
computer science
. Internet pioneers
J. C. R. Licklider
and
Bob Taylor
both completed graduate-level work in psychoacoustics, while
BBN Technologies
originally specialized in consulting on acoustics issues before it began building the first
packet-switched network
.
Licklider wrote a paper entitled "A duplex theory of pitch perception".
[16]
Psychoacoustics is applied within many fields of software development, where developers map proven and experimental mathematical patterns in digital signal processing. Many audio compression codecs such as
MP3
and
Opus
use a psychoacoustic model to increase compression ratios. The success of
conventional audio systems
for the reproduction of music in theatres and homes can be attributed to psychoacoustics
[17]
and psychoacoustic considerations gave rise to novel audio systems, such as psychoacoustic
sound field synthesis
.
[18]
Furthermore, scientists have experimented with limited success in creating new acoustic weapons, which emit frequencies that may impair, harm, or kill.
[19]
Psychoacoustics are also leveraged in
sonification
to make multiple independent data dimensions audible and easily interpretable.
[20]
This enables auditory guidance without the need for spatial audio and in
sonification
computer games
[21]
and other applications, such as
drone
flying and
image-guided surgery
.
[22]
It is also applied today within music, where musicians and artists continue to create new auditory experiences by masking unwanted frequencies of instruments, causing other frequencies to be enhanced. Yet another application is in the design of small or lower-quality loudspeakers, which can use the phenomenon of
missing fundamentals
to give the effect of bass notes at lower frequencies than the loudspeakers are physically able to produce (see references).
Automobile manufacturers engineer their engines and even doors to have a certain sound.
[23]
See also
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Related fields
[
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]
Psychoacoustic topics
[
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References
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]
Notes
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]
- ^
Ballou, G (2008).
Handbook for Sound Engineers
(Fourth ed.). Burlington: Focal Press. p. 43.
- ^
Christopher J. Plack (2005).
The Sense of Hearing
. Routledge.
ISBN
978-0-8058-4884-7
.
- ^
Lars Ahlzen; Clarence Song (2003).
The Sound Blaster Live! Book
. No Starch Press.
ISBN
978-1-886411-73-9
.
- ^
Rudolf F. Graf (1999).
Modern dictionary of electronics
. Newnes.
ISBN
978-0-7506-9866-5
.
- ^
Jack Katz; Robert F. Burkard & Larry Medwetsky (2002).
Handbook of Clinical Audiology
. Lippincott Williams & Wilkins.
ISBN
978-0-683-30765-8
.
- ^
a
b
Olson, Harry F.
(1967).
Music, Physics and Engineering
. Dover Publications. pp. 248?251.
ISBN
978-0-486-21769-7
.
- ^
Kuncher, Milind (August 2007).
"Audibility of temporal smearing and time misalignment of acoustic signals"
(PDF)
.
boson.physics.sc.edu
.
Archived
(PDF)
from the original on 14 July 2014.
- ^
Robjohns, Hugh (August 2016).
"MQA Time-domain Accuracy & Digital Audio Quality"
.
soundonsound.com
. Sound On Sound.
Archived
from the original on 10 March 2023.
- ^
Fastl, Hugo; Zwicker, Eberhard (2006).
Psychoacoustics: Facts and Models
. Springer. pp. 21?22.
ISBN
978-3-540-23159-2
.
- ^
Thompson, Daniel M. Understanding Audio: Getting the Most out of Your Project or Professional Recording Studio. Boston, MA: Berklee, 2005. Print.
- ^
Roads, Curtis. The Computer Music Tutorial. Cambridge, MA: MIT, 2007. Print.
- ^
Lewis, D.P. (2007): Owl ears and hearing. Owl Pages [Online]. Available:
http://www.owlpages.com/articles.php?section=Owl+Physiology&title=Hearing
[2011, April 5]
- ^
Acoustic, Musical (9 March 2015).
"Missing Fundamental"
.
YouTube
.
Archived
from the original on 2021-12-20
. Retrieved
19 August
2019
.
- ^
Sterne, Jonathan (2003).
The Audible Past: Cultural Origins of Sound Reproduction
. Durham: Duke University Press.
ISBN
9780822330134
.
- ^
Cummings, Jim.
"Irv Teibel died this week: Creator of 1970s "Environments" LPs"
.
Earth Ear
. Retrieved
18 November
2015
.
- ^
Licklider, J. C. R. (January 1951).
"A Duplex Theory of Pitch Perception"
(PDF)
.
The Journal of the Acoustical Society of America
.
23
(1): 147.
Bibcode
:
1951ASAJ...23..147L
.
doi
:
10.1121/1.1917296
.
Archived
(PDF)
from the original on 2016-09-02.
- ^
Ziemer, Tim (2020). "Conventional Stereophonic Sound".
Psychoacoustic Music Sound Field Synthesis
. Current Research in Systematic Musicology. Vol. 7. Cham: Springer. pp. 171?202.
doi
:
10.1007/978-3-030-23033-3_7
.
ISBN
978-3-030-23033-3
.
S2CID
201142606
.
- ^
Ziemer, Tim (2020).
Psychoacoustic Music Sound Field Synthesis
. Current Research in Systematic Musicology. Vol. 7. Cham: Springer.
doi
:
10.1007/978-3-030-23033-3
.
ISBN
978-3-030-23032-6
.
ISSN
2196-6974
.
S2CID
201136171
.
- ^
"Acoustic-Energy Research Hits Sour Note"
. Archived from
the original
on 2010-07-19
. Retrieved
2010-02-06
.
- ^
Ziemer, Tim; Schultheis, Holger; Black, David; Kikinis, Ron (2018). "Psychoacoustical Interactive Sonification for Short Range Navigation".
Acta Acustica United with Acustica
.
104
(6): 1075?1093.
doi
:
10.3813/AAA.919273
.
S2CID
125466508
.
- ^
CURAT.
"Games and Training for Minimally Invasive Surgery"
.
CURAT
. University of Bremen
. Retrieved
15 July
2020
.
- ^
Ziemer, Tim; Nuchprayoon, Nuttawut; Schultheis, Holger (2019). "Psychoacoustic Sonification as User Interface for Human-Machine Interaction".
International Journal of Informatics Society
.
12
(1).
arXiv
:
1912.08609
.
doi
:
10.13140/RG.2.2.14342.11848
.
- ^
Tarmy, James (5 August 2014).
"Mercedes Doors Have a Signature Sound: Here's How"
.
Bloomberg Business
. Retrieved
10 August
2020
.
Sources
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External links
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