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An audio frequency or audible frequency (AF) is a periodic vibration whose frequency is audible to the average human. The SI unit of frequency is the hertz (Hz). It is the property of sound that most determines pitch .
This is a list of the fundamental frequencies in hertz (cycles per second) of the keys of a modern 88-key standard or 108-key extended piano in twelve-tone equal temperament, with the 49th key, the fifth A (called A 4), tuned to 440 Hz (referred to as A440). [1] [2] Every octave is made of twelve steps called semitones.
For 50 Hz systems such as PAL each frame is shown twice. Since 50 is not exactly 2×24, the movie will run 50/48 = 4% faster, and the audio pitch will be 4% higher, an effect known as PAL speed-up . This is often accepted for simplicity, but more complex methods are possible that preserve the running time and pitch.
For instance, a note vibrating at 200 Hz and a note vibrating at 300 Hz (a perfect fifth, or 3 / 2 ratio, above 200 Hz) add together to make a wave that repeats at 100 Hz: Every 1 / 100 of a second, the 300 Hz wave repeats three times and the 200 Hz wave repeats twice. Note that the combined wave repeats at 100 Hz, even though ...
For example, if the fundamental frequency is 50 Hz, a common AC power supply frequency, the frequencies of the first three higher harmonics are 100 Hz (2nd harmonic), 150 Hz (3rd harmonic), 200 Hz (4th harmonic) and any addition of waves with these frequencies is periodic at 50 Hz.
Waveform Audio File Format (WAVE, or WAV due to its filename extension; [3] [6] [7] pronounced / w æ v / or / w eɪ v / [8]) is an audio file format standard for storing an audio bitstream on personal computers.
A timpani might be tuned to produce sound most strongly at 200, 302, 398, and 488 Hz, for instance, implying a missing fundamental at 100 Hz (though the actual dampened fundamental is 170 Hz). [ 19 ] A violin 's lowest air and body resonances generally fall between 250 Hz and 300 Hz.
A vibration in a string is a wave. Resonance causes a vibrating string to produce a sound with constant frequency, i.e. constant pitch. If the length or tension of the string is correctly adjusted, the sound produced is a musical tone. Vibrating strings are the basis of string instruments such as guitars, cellos, and pianos.