Pitch

The pitch of a note is the frequency of its vibrations. The exact pitch of notes has varied over the years and nowadays differs to some extent between continent and continent or even between orchestra and orchestra. Earlier pitches were generally lower, but not necessarily standardised. Perfect pitch is the ability to distinguish the pitch of a note, according to generally accepted nomenclature. Relative pitch is the ability to distinguish the pitch of one note with relation to another, given note.

Provided by http://www.naxos.com/education/glossary.asp?char=P-R#

Pitch (Wikipedia)
Pitch represents the perceived fundamental frequency of a sound.[1] It is one of the four major auditory attributes of sounds along with loudness, timbre and sound source location. When the actual fundamental frequency can be precisely determined through physical measurement, it may differ from the perceived pitch because of overtones, also known as upper partials, harmonic or otherwise. The human auditory perception system may also have trouble distinguishing frequency differences between notes under certain circumstances. According to ANSI acoustical terminology, it is the auditory attribute of sound according to which sounds can be ordered on a scale from low to high

Perception of pitch
Pitch is a subjective sensation in which a listener assigns perceived tones to relative positions on a musical scale based primarily on the frequency of vibration. The just-noticeable difference (jnd, the threshold at which a change is perceived) depends on the tone's frequency and is about 4.3 cents (1 cent = 1 hundredth of a semitone) or about 0.36 Hz in frequency within the octave of 1,000–2,000 Hz but within the octave 62–125 Hz the jnd is much coarser with some 40 cents or about 2 Hz between perceived pitch changes. The jnd is typically tested by playing two tones in quick succession with the listener asked if there was a difference in their pitches.[2] The jnd becomes smaller if the two tones are played simultaneously as the listener is then able to discern beat frequencies. The total number of perceptible pitch steps in the range of human hearing is about 1,400; the total number of notes in the equal-tempered scale is 120.[2]
Pitch depends to lesser degree on the sound pressure level (loudness, volume) of the tone, especially at frequencies below 1,000 Hz and above 2,000 Hz. The pitch of lower tones gets lower as sound pressure increases. For instance, a tone of 200 Hz that is very loud will seem to be one semitone lower in pitch than if it is just barely audible. The pitch of higher tones gets higher as the sound gets louder.[2] In this way, pitch perception is like other human senses which respond to the intensity of the stimulus as stated in the Weber–Fechner law.
The relative perception of pitch can be fooled, resulting in "aural illusions". There are several of these, such as the tritone paradox, but most notably the Shepard scale, where a continuous or discrete sequence of specially formed tones can be made to sound as if the sequence continues ascending or descending forever.

Perception of pitch
Pitch is a subjective sensation in which a listener assigns perceived tones to relative positions on a musical scale based primarily on the frequency of vibration. The just-noticeable difference (jnd, the threshold at which a change is perceived) depends on the tone's frequency and is about 4.3 cents (1 cent = 1 hundredth of a semitone) or about 0.36 Hz in frequency within the octave of 1,000–2,000 Hz but within the octave 62–125 Hz the jnd is much coarser with some 40 cents or about 2 Hz between perceived pitch changes. The jnd is typically tested by playing two tones in quick succession with the listener asked if there was a difference in their pitches.[2] The jnd becomes smaller if the two tones are played simultaneously as the listener is then able to discern beat frequencies. The total number of perceptible pitch steps in the range of human hearing is about 1,400; the total number of notes in the equal-tempered scale is 120.[2]
Pitch depends to lesser degree on the sound pressure level (loudness, volume) of the tone, especially at frequencies below 1,000 Hz and above 2,000 Hz. The pitch of lower tones gets lower as sound pressure increases. For instance, a tone of 200 Hz that is very loud will seem to be one semitone lower in pitch than if it is just barely audible. The pitch of higher tones gets higher as the sound gets louder.[2] In this way, pitch perception is like other human senses which respond to the intensity of the stimulus as stated in the Weber–Fechner law.
The relative perception of pitch can be fooled, resulting in "aural illusions". There are several of these, such as the tritone paradox, but most notably the Shepard scale, where a continuous or discrete sequence of specially formed tones can be made to sound as if the sequence continues ascending or descending forever.

Provided by: http://en.wikipedia.org/wiki/Pitch_(music)