8ve Oscillator (Octave Oscillator)
Turn your iPhone/iPod touch into a professional test oscillator with instant octave frequency values. It can be used for quick hearing testing, room acoustic testing and equipment testing. Arbitrary frequency values between 20 Hz and 20 kHz can also be entered using a text box. Output level control is calibrated in decibels on either a 1dB, 3dB, 6dB or 10dB steps.
Octave oscillator test waveforms include sine, pulse, square, sawtooth and triangular waves at octave fundamental frequencies covering the hearing range (125 Hz, 250 Hz, 500 Hz, 1 kHz, 2 kHz, 4 kHz, 6 kHz and 16 kHz) or they can be set to arbitrary values. These frequencies (except 16 kHz) are used in hearing testing as well as for testing room acoustics and equipment testing. The 16 kHz is a special case; this frequency is used as a "teen scarer" or "mosquito" tone because it can typically only be heard by those under 25 years of age.
The signals are generated at CD quality using 16 bit PCM "wav" format harmonic synthesis (within the Nyquist rate) at a sampling frequency of 44.1 kHz. The signal plays until the user presses the "Stop" button.
The output level is controlled in using a calibrated decibel attenuator in selectable steps of either 1 dB, 3 dB, 6 dB or 10 dB; (1 dB is about the minimum step we can hear; -3 dB (+3 dB) is an intensity halving (doubling); -6 dB (+6 dB) is an acoustic pressure halving (doubling) and -10 dB (+10 dB) is an average halving (doubling) in perceived loudness).