1. Alexis Baskind
Psychoacoustics 1
Introduction, the ear
Alexis Baskind, https://alexisbaskind.net

2. Alexis Baskind
Psychoacoustics 1 – Introduction, the ear
Course series
Fundamentals of acoustics for sound engineers and music producers
Level
undergraduate (Bachelor)
Language
English
Revision
January 2020
To cite this course
Alexis Baskind, Psychoacoustics 1 – The ear, course material, license: Creative
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Psychoacoustics 1 – Introduction, the ear
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3. Alexis Baskind
Outline
1. What is psychoacoustics?
2. The physiology of the ear
3. Hearing damages
Psychoacoustics 1 – Introduction, the ear

4. Alexis Baskind
What is Psychoacoustics?
• Psychoacoustics is a sub-branch of psychophysics,
a branch of science concerned with the
relationships between physical stimuli and
subjective mental phenomena like perception.
• Psychoacoustics focuses on the auditory
perception: how a sound signal with given
characteristics is perceived by the ear?
Psychoacoustics 1 – Introduction, the ear

5. Alexis Baskind
What is Psychoacoustics?
• There is an equivalent of several objective
characteristics of sound in the auditory
perception, for example:
– Level => Loudness
– Fundamental Frequency => Pitch
– Frequency Relationships => Intervals
– Amount of high frequencies in the spectrum
=> Brightness
• The relation between objective parameters and
their perception by audition is however rarely easy
Psychoacoustics 1 – Introduction, the ear

6. Alexis Baskind
Why is Psychoacoustics important for
Music Production?
• Many techniques used in music production result
from findings from psychoacoustics
• The results of research in psychoacoustics tell us,
what we can hear and what we cannot
Psychoacoustics 1 – Introduction, the ear

7. Alexis Baskind
Why is Psychoacoustics important for
Music Production?
• In music production, it’s a mistake to consider only
objective characteristics of sound and signal, since
the relationship between those and hearing can
sometimes be very complex
• It is very useful to know how the ear system
works, in order to reach quicker a given goal while
producing music
Psychoacoustics 1 – Introduction, the ear

8. Alexis Baskind
Outline
1. What is psychoacoustics?
2. The physiology of the ear
3. Hearing damages
Psychoacoustics 1 – Introduction, the ear

9. Alexis Baskind
The physiology of the ear
Psychoacoustics 1 – Introduction, the ear
Video Laura J. Martin, « Hearing and the Cochlea », MedilinePlus, National Library of Medicine
MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National
Institutes of Health (NIH), and other government agencies and health-related organizations.

10. Alexis Baskind
The physiology of the ear
Psychoacoustics 1 – Introduction, the ear
• The ear has two tasks:
– to transform ear pressure information into nerve
impulses
– to participate to the sense of balance (thanks to the so-
called vestibular mechanism in the inner ear)
• The ear is made of
three parts: outer,
middle and inner ear

11. Alexis Baskind
The physiology of the ear
The ear conch and the ear canal collect sound (like a
funnel) and conduct it until the ear drum. Moreoever,
the ear conch filters sound according to the direction
of arrival (see „Spatial Hearing“)
Psychoacoustics 1 – Introduction, the ear

12. Alexis Baskind
The physiology of the ear
Psychoacoustics 1 – Introduction, the ear
The eardrum vibrates with sound pressure, and
transmits this vibration to the bones in the
middle ear

13. Alexis Baskind
The physiology of the ear
Psychoacoustics 1 – Introduction, the ear
The bones in the middle ear (called malleus,
incus and stapes) make the oval window
vibrate…

14. Alexis Baskind
The physiology of the ear
The main function of the middle ear is to optimize the
sound transfer from a gaseous outer medium (air) to a
liquid inner medium. Without it, only a fraction of the
sound energy would be transmitted to the inner ear.
Psychoacoustics 1 – Introduction, the ear

15. Alexis Baskind
The physiology of the ear
Psychoacoustics 1 – Introduction, the ear
…thus transmitting the vibration to the organ of
Corti in the cochlea (in the inner ear)

16. Alexis Baskind
The physiology of the ear
Psychoacoustics 1 – Introduction, the ear
The vibration of the organ of Corti depends on
the frequency. Low frequencies have to travel all
the organ to reach the end => Frequency
decomposition (like a filter bank)

17. Alexis Baskind
The physiology of the ear
Psychoacoustics 1 – Introduction, the ear
The organ of Corti has tiny hairs called hair cells
which role is to transform the vibration into nerve
impulses that will be transmitted to the the central
nervous system.

18. Alexis Baskind
Outline
1. What is psychoacoustics?
2. The physiology of the ear
3. Hearing damages
Psychoacoustics 1 – Introduction, the ear

19. Alexis Baskind
Hearing damages
Psychoacoustics 1 – Introduction, the ear
The hair cells can hardly regenerate: when
they’re damaged, its finished
=> Protect your ears !
Organ of Corti (of a mouse)
in good condition
The same after an exposure
to a very loud noise

20. Alexis Baskind
Hearing damages
Psychoacoustics 1 – Introduction, the ear
Hearing loss can result (among others) of:
• Long-term exposure to loud sounds, or short-term
exposure to very loud sounds:
Ex: . a gunshot (140-170 dB SPL) can damage hearing
immediately
. an ambulance siren (120 dB SPL) can damage hearing after 7
minutes exposure per day
. A loud rock music concert (110-130 dB SPL) can damage
hearing after 3.5-30 minutes exposure per day
. Listening to iPod or similar with earphones at maximum volume
(> 100 dB SPL) can damage hearing after 5 minutes exposure per day
. Listening to iPod or similar with earphones in the street
(≈85-95 dB SPL) can damage hearing after 4 hours exposure per day

21. Alexis Baskind
Hearing Damages and Ear Fatigue
• Producing Music every day may not entail long-term
hearing damages, but is anyway quite exhausting
for the ear.
• With increasing ear fatigue, the accuracy of the
perception and the attention decrease
This means: regular breaks are important!
Psychoacoustics 1 – Introduction, the ear

22. Alexis Baskind
Hearing damages
Psychoacoustics 1 – Introduction, the ear
Hearing loss can result (among others) of:
• High pressure differences (air plane, deep water,
high altitudes)
• Age
• Genetics
• Diseases
• Drugs
• Some medications and chemicals (classified as
“ototoxic”: some antibiotics, aspirin, quinine...

23. Alexis Baskind
Conclusion
• The ear is made of three parts: outer, middle and inner
ear
• Outer and middle ear aim at adapting and transmitting
sound as vibrations to the cochlea in the inner ear
• The hair cells in the cochlea transforms those vibrations
into nerve impulses
• The Cochlea does a “frequency analysis” of the sound
• The hair cells are fragile and cannot be regenerated,
except (and only partly) in the first hours after an ear
trauma
• An ear injury is an absolute emergency and needs a
quick and professional treatment
Psychoacoustics 1 – Introduction, the ear