People can perceive sound frequency {pitch, sound}|.
frequency
People can hear ten frequency octaves, from 20 Hz to 20,000 Hz. Lowest frequencies, 20 Hz to 30 Hz, are also highest vibrations detectable by touch.
Shortest hair-cell hair lengths detect highest frequencies. High-frequency tones vibrate basilar-membrane stiff narrow end, far from oval window. Above 3000 Hz, higher hearing neurons respond to frequency, tone pattern, or intensity range.
Low-frequency tones activate all hair cells, with greater activity near oval window and its long-hair hair cells.
sensitivity
People are most sensitive at frequency 1800 Hz.
neuron firing
Maximum neuron firing rate is 800 Hz. After sound frequency and firing rate reach 800 Hz, firing rate drops abruptly, and more than one neuron carries sound-frequency information. After sound frequency and firing rate reach 1600 Hz, firing rate drops abruptly.
Auditory neurons have frequency {characteristic frequency} (CF) at which they are most sensitive. The characteristic frequency is at the maximum of the frequency-intensity spectrum (threshold tuning curve). For CF = 500 Hz at 0 dB, 1000 Hz is at 80 dB, and 200 Hz is at 50 dB. For CF = 1100 Hz at 5 dB, 1500 Hz is at 80 dB, and 500 Hz is at 50 dB. For CF = 2000 Hz at 5 dB, 3500 Hz is at 80 dB, and 500 Hz is at 80 dB. For CF = 3000 Hz at 5 dB, 3500 Hz is at 80 dB, 700 Hz to 2000 Hz is at 50 dB, and 500 Hz is at 80 dB. For CF = 8000 Hz at 5 dB, 9000 Hz is at 80 dB, 1000 Hz to 3000 Hz is at 60 dB, and 500 Hz is at 80 dB. For CF = 10000 Hz at 5 dB, 10500 Hz is at 80 dB, 5000 Hz is at 80 dB, 1000 Hz to 2000 Hz is at 60 dB, and 500 Hz is at 80 dB.
Auditory-nerve channels carry frequency-range {critical band} information.
For 100-Hz to 6000-Hz sound stimuli, basilar membrane has electric pulses, with same frequency and intensity, caused by potentials from all hair cells, that do not fatigue.
For 20-Hz to 900-Hz sound stimuli, auditory-neuron axons have electric pulses {microphonic electric pulse}, measured in cochlear nerve, with same frequency and intensity [Saul and Davis, 1932]. For 900-Hz to 1800-Hz sound stimuli, auditory-neuron axons have electric pulses with same frequency and one-half intensity. For 1800-Hz to 2700-Hz sound stimuli, auditory-neuron axons have electric pulses with same frequency and one-third intensity. For above-2700-Hz sound stimuli, auditory-neuron axons have electric pulses that do not correlate with frequency and intensity. Perhaps, auditory nerve uses summed potentials of microphonic-electric-pulse envelopes.
For below-500-Hz sound stimuli, auditory-neuron-axon signals have same frequency and phase {phase locking, hearing}.
Similar frequencies group together to make increasing loudness {recruitment, hearing}.
Tones that share one octave have perceivable sound features {tone chroma}.
Tone frequency determines low or high pitch {tone height}.
Noise or tones within two octaves of stimulus frequency can interfere with stimulus perception {critical band masking}. Pure tones mask high frequencies more than low frequencies, because higher frequencies activate smaller basilar-membrane regions. Complex tones mask low frequencies more than high frequencies, because lower frequencies have more energy than higher frequencies [Sobel and Tank, 1994].
Previous-tone {preceding tone} intensity-frequency spectrum affects neuron current-tone response.
Different later tone can decrease auditory-neuron firing rate {two-tone suppression}.
At each audible frequency, people have an intensity threshold {audibility curve}.
At each audible frequency, specific sound-pressure levels (SPL) cause people to hear equal loudness {equal loudness curve}.
At constant amplitude, auditory-neuron firing rate depends on frequency {isointensity curve}. For amplitude 20 dB at characteristic frequency, firing rate is 180 per second. For amplitude 20 dB at 500 Hz below or 500 Hz above characteristic frequency, firing rate is 50 per second. For amplitude 20 dB at 1300 Hz to 1400 Hz above characteristic frequency, auditory neurons have spontaneous firing rate.
At each frequency, people have a sound-intensity threshold {threshold tuning curve}.
Same-intensity-and-pitch sounds can have different harmonics {timbre, sound}|. Rapid timbre changes are difficult to perceive.
Clear tones {clarity, tone} have narrow frequency band. Unclear tones have wide frequency band.
Full tones {fullness, tone} have many frequency resonances. Shallow tones have few frequency resonances.
Shrill tones {shrillness} have higher frequencies. Dull tones have lower frequencies.
Sounds with many high-frequency components seem sharp or strident {stridency}. Tones with mostly low-frequency components seem dull or mellow {mellowness}.
1-Consciousness-Sense-Hearing-Physiology
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Date Modified: 2022.0225