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The human range is commonly given as 20 to 20,000 Hz, [3] [4] [note 1] although there is considerable variation between individuals, especially at high frequencies, and a gradual loss of sensitivity to higher frequencies with age is considered normal. Sensitivity also varies with frequency, as shown by equal-loudness contours.
In telephony, the usable voice frequency band ranges from approximately 300 to 3400 Hz. [2] It is for this reason that the ultra low frequency band of the electromagnetic spectrum between 300 and 3000 Hz is also referred to as voice frequency, being the electromagnetic energy that represents acoustic energy at baseband.
The hearing of older adults is shown to be significantly less sensitive than that of younger adults at frequencies of 4000 and 8000 Hz, corresponding approximately to the piano keys and tones of b′′′′ (B7) and b′′′′′ (B8), respectively. B8 is near the high end of the piano frequency range.
1 hertz (Hz) 1 to 1.66 Hz: Approximate frequency of an adult human's resting heart beat: 1 Hz: 60 bpm, common tempo in music 2 Hz: 120 bpm, common tempo in music ~7.83 Hz: Fundamental frequency of the Schumann resonances: 10 1: 10 hertz 10 Hz: Cyclic rate of a typical automobile engine at idle (equivalent to 600 rpm) 12 Hz
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Audiogram. An audiogram is a graph that shows the audible threshold for standardized frequencies as measured by an audiometer.The Y axis represents intensity measured in decibels (dB) and the X axis represents frequency measured in hertz (Hz). [1]
The mel scale (after the word melody) [1] is a perceptual scale of pitches judged by listeners to be equal in distance from one another. The reference point between this scale and normal frequency measurement is defined by assigning a perceptual pitch of 1000 mels to a 1000 Hz tone, 40 dB above the listener's threshold.
Stage 2 is characterized by sleep spindles (intermittent clusters of waves at sigma frequency i.e. 12–14 Hz) and K complexes (sharp upward deflection followed by slower downward deflection). Stage 3 sleep has more sleep spindles. [24] [25] [26] Stage 3 has very high amplitude delta waves (0–4 Hz) and is known as slow wave sleep. [27]