What each waveform is for
A sine wave is a single frequency and nothing else, which makes it the right tool for testing a speaker or checking hearing. Square and sawtooth waves contain a whole series of harmonics, which is what makes them useful for testing a system’s response across a range and unpleasant to listen to.
Testing hearing, carefully
Human hearing nominally spans 20Hz to 20kHz, and the top end declines with age — many adults over forty cannot hear above 15kHz. A sweep will show roughly where yours stops.
Two warnings that matter. Start at a low volume: a tone you cannot hear may still be loud enough to damage hearing, and consumer headphones and laptop speakers roll off at both extremes, so failing to hear 18kHz may be the equipment rather than you. This is a curiosity, not an audiogram.
Other uses
Checking stereo channels are wired the right way round. Finding a room’s resonant frequencies by sweeping slowly and listening for where it booms. Tuning an instrument against a reference — A4 is 440Hz by convention, though some orchestras tune to 442 or 443.
Frequently asked questions
Which waveform should I use?
Sine for testing anything, since it is a single frequency. Square and sawtooth carry harmonics, useful for testing response across a range.
I cannot hear above 15kHz. Is that normal?
Yes for most adults over forty. It may also be your speakers or headphones, which roll off at both extremes.
Is this a hearing test?
No. Consumer equipment and ambient noise both affect the result. A real audiogram is done in a controlled setting with calibrated equipment.
Something wrong with this tool, or an idea for it? Tell us