Pitch Perception Or, what happens to the sound from the air outside your head to your brain….

Sensitivity of the human ear: varies with pitch varies with loudness

Perception of one pitch Most sensitive around 3000 Hz. Least sensitive at high and low ends High frequency sensitivity decreases with age (and damage to ear)

Frequencies important for music Frequency range of piano Hz. Frequency range of voice fundamentals: low C for bass - 65 Hz. high F for soprano Hz. (important overtones are higher)

Pitch is determined by hair cells on basilar membrane 2/3 of basilar membrane accounts for range of Hz. Membrane has a logarithmic scale; jump of one octave anywhere in range is about the same jump on membrane (3.5-4 mm)

“Just Noticable Difference” When presented with two tones in succession, when are they the same and when are they different? Slow change: detection of.5% at 2000 Hz. (only 10 Hz.!) 1% at 350 Hz. 3% at 100 Hz. (Try this with oscillator) Fast change: much more sensitive

Absolute pitch (also known as “perfect” pitch) Ability to identify the note name of a sound, or to reproduce a specific note, without reference to an external standard. The above skill sometimes called “tone AP”, where the skill to recognize whether a piece of music is played in the correct key is “piece AP”

One person in 10,000 claims to have it Absolute pitch is not necessarily “perfect”: people can identify % of midrange tones (chance level is 1/12 or 8.3%) Develops during early life; nature vs. nurture source hard to determine Composers with AP include Mozart, Scriabin, Messiaen, Boulez

Absolute pitch can be a negative: playing or singing in a key other than written (transposed) Playing or singing in a group which strays off pitch constant awareness of pitch labels hurts enjoyment of music

“Relative pitch”: ability of musicians to determine note name with external standard present This is an expected skill for trained musicians; some will be better than others

Perception of multiple tones, related to “consonance” When two pure tones are heard, one stays the same and the second one can be varied in pitch: 1. When second pitch is close, most people think the resultant sound is “consonant” 2. As second sound gets farther away, very few people think sound is consonant 3. After two sounds get to around the distance of a minor third, most people again think the resultant sound is consonant

Perception of multiple tones When two pure tones are heard, one stays the same and the second one can be varied in pitch: 1. Very close  sounds like one tone, with beats 2. After passing “limit of frequency discrimination”  sounds like two tones with “roughness” 3. After passing “critical band”  sounds like two tones sounding smooth

These effects depend on how high the tones are Phenomenon is true for both tones heard by one or two ears; When 2 tones are separated and fed into different ears, roughness disappears

We infer that effect comes from each tone exciting a “range” on the basilar membrane (not one single point), and that the two tones interfere with each other This supports the “place” theory of response of the basilar membrane

Combination Tones strong intensityHeard from two tones of strong intensity “Difference tone” is f 2 -f 1 When two tones are a fifth apart, the difference tone is 1 octave below f 1 Other tones made from 2f 1 -f 2 and 3f 1 -2f 2 Thought to come from “nonlinear” distortion of the primary wave form stimulus in cochlea - the vibration of the additional tone is present in cochlea (try with 2 oscillators?)

Second order effects Beats created from two tones an octave apart, mistuned slightly (try this with oscillators)

Fundamental tracking The processing system supplies the “missing fundamental” from a set of upper harmonics Example: two tones a fifth apart  another note heard 1 octave below f 1 Two tones a third apart  another note heard 2 octaves below f 1 The result is the same as difference tone but is not the same phenomenon: vibration of additional tone is not present in the cochlea

What is happening here?? Fundamental tracking is shown to happen even when pitches are fed into separate ears The pitch perception process is so used to hearing complex tones with a fundamental and upper overtones (from harmonic series) that if it only hears some of the overtones, it supplies the fundamental

Auditory system can perceive the overall repetition rate of mixed sounds, which is the frequency of the “missing” f 0