Hearing and Auditory Perception: Part 3

The Human Ear

• The main function of the Pinna is to collect and direct sound waves into the ear canal.

Sound Conversion

• The cochlea is responsible for converting motion to neural activity in the human ear.
• The primary function of the cochlea is to convert acoustic energy into neural signals.

Transduction

• The eardrum performs transduction from acoustic waves to mechanical pressure waves.

Auditory Nerve

• The auditory nerve is responsible for transmitting neural signals from the cochlea to the brain.

Inner Hairs

• Inner hairs are located in the cochlea and are responsible for converting mechanical pressure waves into neural signals.

Loudness and Sound Pressure Level

• Loudness is directly proportional to the sound pressure level.
• A 10 dB increase in sound pressure level corresponds to a perceived doubling of loudness.

Threshold of Audibility

• The threshold of audibility is the minimum sound pressure level that can be detected by the human ear.

Equal-Loudness-Level Contours

• Equal-loudness-level contours represent the sound pressure levels at different frequencies that are perceived as equally loud.

Loudness and Frequency

• Low frequencies must be more intense than mid-range frequencies to be perceived equally loud.
• This is because the human ear is less sensitive to low frequencies.

Determinant of Equal-Loudness-Level Contours

• The equal-loudness-level contours are determined by the frequency response of the human ear.

Frequency Range

• The frequency range of 100Hz-6KHz is significant because it includes the majority of speech frequencies.

Pitch and Frequency

• Pitch is directly proportional to the frequency of a pure tone, but this relationship is non-linear.
• The mel scale is a non-linear frequency scale that more accurately represents the relationship between pitch and frequency.

Bandpass Filters

• It is possible to span the range of 0-20 kHz with multiple bandpass filters.

Critical Bandwidth

• A critical bandwidth of 160 Hz centered on 1 kHz maps into approximately 3.5 mels.

Masking

• Masking occurs when a sound is made inaudible by the presence of another sound that is closer to the audibility threshold.

Critical Bands

• Critical bands are important in auditory perception because they determine the frequency ranges within which sounds can be masked.

Pitch Perception

• Only sounds with a frequency above 50 Hz and below 20,000 Hz are perceived to have pitch.