S1W4-Hear

Question 1

What is sound?

Answer 1

Pressure wave generated by vibrating air molecules.

Sound waves are small changes in pressure that travel in waves of rarefaction and condensation

Question 2

Speed of sound

Answer 2

Air : 340 m/s
Water : 1500 m/s
Glass: 5300 m/s

Question 3

Condensation

Answer 3

Regions of higher molecular density - Air pressure greater than atmospheric

Question 4

Rarefaction

Answer 4

Regions of lower molecular density - Air pressure less than atmospheric

Question 5

Frequency

Answer 5

Linked to perceptual pitch.

Number of cycles per second.

Measured in Hertz (Hz).

Question 6

Amplitude

Answer 6

Linked to perceptual loudness.

Sound pressure level.

Higher pressure means higher amplitude (louder).

Measured in decibels (dB).

Question 7

Pure tones

Answer 7

Sounds that consist of a single sine wave.

A consistent sound like a tuning fork.

Question 8

Complexity

Answer 8

Most sounds are complex sounds.

Made up of one fundamental frequency and several harmonic frequencies.

Higher harmonics are pure tones with frequencies that are multiples (x2, x3 etc.) of the fundamental tone.

Question 9

Magnitude estimation procedure

Answer 9

Participants judged the loudness of a sound relative to 40db tone which was assigned value of 1.

A tone that was judged 10 times louder than the 40db one was given loudness of 10 (40-50db).

Question 10

Audibility curve

Answer 10

Loudness also depends on frequency.

The curve shows the threshold for hearing vs. frequency and db.

Audible range: 20hz - 20khz.

Sensitivity greatest from 500hz-5khz meaning db can be low and we can still hear in this area.

Known as threshold of hearing.

Question 11

Threshold of hearing

Answer 11

Above the audibility curve: can start to feel sounds.

120db+ damages hearing

Question 12

Pitch

Answer 12

Psychological property of auditory sensation in which sounds may be ordered on a musical scale (from low to high).

Closely related to the physical property of fundamental frequency.

Question 13

Timber

Answer 13

When two tones have the same loudness, pitch and duration, but sound different.

Closely related to the harmonic structure of a tone.

Question 14

Fundamental frequency

Answer 14

Repetition rate of the sound waveform.

Low fundamental frequencies associated with low pitches etc.

Question 15

Tone height

Answer 15

Perception of increasing pitch that accompanies increases in fundamental frequency.

Question 16

Outer ear

Answer 16

Gathers sound.

Sound waves pass through pinna and auditory canal.

Auditory canal protects the eardrum (tympanic membrane).

Enhances sounds through resonance.

Question 17

Middle ear

Answer 17

Vibration from eardruom is transmitted to middle ear.

Vibrations travel through each of the ossicles (three smallest bones: malleus, incus and stapes).

Stapes transmits vibrations to inner ear by puhing on membrane covering the oval window.

The ossicles transform the vibrations to deal with the fluid filled inner ear.

Question 18

Inner ear

Answer 18

Where auditory receptors are located.

Base near outer ear and apex further in.

Vibrations sent to cochlea by the movement of the oval window.

Cochlea partition separates scala vestibuli (top) and scala tympani (bottom) and transforms vibrations into electricity.

Partition contains organ of corti.

Question 19

Organ of corti

Answer 19

Receptor organ containing 16k hairs in four rows (one inner, 3 outer).

Question 20

Resonance

Answer 20

Happens in auditory canal.

Reflects sounds from back of auditory canal so they interact with new incoming sounds.

Reinforces sound’s frequencies.