Excellent for teaching and increasing understanding of
sound generation, human hearing range, hearing loss
effects, and turns your device into a cheap test
oscillator!
Octave Oscillator with Noise (8ve Oscillator) produces test signals (sine, square, pulse, triangular, sawtooth and white noise) at a selection of octave spaced fundamental frequencies (except the noise!) and arbitrary fundamental frequency value entry across the usually quoted overall frequency range of human hearing (20 Hz to 20 kHz) via a text field.
As well as by text entry, the fundamental frequency can be selected at the octave values for convenience (going up or down by one octave doubles or halves the frequency respectively) that are typically used for acoustic testing of rooms, equipment testing and clinical hearing tests: 125 Hz, 250 Hz, 500 Hz, 1 kHz, 2 kHz, 4 kHz and 8 kHz. The remaining available fundamental frequency (16 kHz) is not used for acoustic or hearing tests but it is an octave above 8 kHz and is close to the frequency used for "mosquito" or "teen scarer" devices; it is usually only audible to those under 25 years.
The output level can be varied with a decibel (dB) calibrated volume control arranged to allow the selection of dB step value as 1 dB, 3 dB, 6 dB or 10 dB. These enable the effect of stepping the output level in dB to be experimented with: 1 dB is about the minimum step size we can hear; a -3 dB (+3 dB) step is a halving (doubling) in sound intensity; a -6 dB (+6 dB) step is a halving (doubling) in sound pressure; and a -10 dB (+10 dB) step is a halving (doubling) in perceived loudness.
Hearing awareness: Please be aware that listening to loud sounds can damage your hearing and use HarmSyn with care and due consideration for your own ears as well as the ears of others. Please also bear in mind that if you cannot hear a sound it does not mean that others around you cannot hear it (everyone will lose high frequency hearing with age - an effect known as presbycusus) - this is especially true of the 16 kHz output which can be very irritating to those who can hear it (this is why it is used as a "teen scarer").
More details about human hearing can be found in: Howard and Angus, Acoustics and psychoacoustics, 4th Edition, Oxford: Focal Press, 2009, ISBN: 978-0-240-52175-6.
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