Hearing

Smallest time lag between which the ear can distinguish two sounds.
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Terms in this set (9)
Smallest time lag between which the ear can distinguish two sounds.
10us
The ear can distinguish between two sounds whose frequencies differ by x %
0.5%
What is a decibel?
A decibel (1/10th of a bel) is a ratio expressed relative to a reference value on a logarithmic scale.

If the sound is the same as the reference value (threshold for human hearing) then the sound is log1 = 0dB.

The threshold for pain is 140dB.

If the specified sound has a negative value, then the sound is less than the reference (it is not a negative sound!).

IMPORTANT NOTE:
Double pressure (Pa) => increase by 6dB
Double power (W/m^-2) => increase by 3dB

dB SPL = 20 Log10(Pressure/20 μPa)
What does the peripheral auditory system consist of?
1) Ear
- Outer ear: pinna, external auditory meatus
- Middle ear: tympanic membrane, ossicles, middle ear cavity
- Inner ear: cochlea
2) Auditory nerve
Azimuth
A horizontal angle between the origin and the point of interest. Used in measuring the angles of spherical coordinates.

When the azimuthal location is 90 degrees, the sound is directly in line with the left pinna.
What are three functions of the middle ear?
1. Impedance matching
(between air and cochlear fluids)
2. Protection from loud sounds
3.
What does the outer ear consist of?
1. The pinna
Assists in sound localisation by modifying the spectra of sounds in a space-dependent manner
2. The external auditory meatus (ear canal)
Gain of sound through ear canal (2-3cm long) depends upon the location - aids sound localisation
How can you distinguish between conductive hearing loss and sensorineural hearing loss.
Conductive hearing loss occurs when the middle ear cavity fills with fluid (common in small children)

Sensorineural hearing loss results from damage to cochlea or auditory pathway.

Rinne test distinguishes between the two:
- Alternately place tuning fork at mastoid process and entrance to ear canal (EAM)
- If conductive then hear
What is the function of the middle ear muscles?
- Contract to dampen the oscillations of the vibrations of the ossicles
- Thereby reducing the acoustic signal that reaches the ears
- Include the tensor tympani and stapedius