What Does "Audible" Mean in Audio? The Frequency Range of Human Hearing

A sound is audible when two things are true at once: its frequency falls inside the band human ears respond to, and its level at that frequency is above the threshold of hearing. Both conditions matter. A 30 Hz tone played quietly is inside the band but may still be inaudible; an intense vibration at 5 Hz can be felt without being heard at all.

The conventional band

The audible band is usually stated as roughly 20 Hz to 20,000 Hz (20 kHz). Frequency is the number of pressure cycles per second, measured in hertz, and it is the property people perceive as pitch; amplitude is the size of the pressure change, and it is the property people perceive as loudness. The National Park Service explainer on sound sets out both properties in those terms.

Two labels attach to the regions outside the band:

• Infrasound — below the low end of the band.
• Ultrasound — above the high end.

The 20 Hz–20 kHz figure is a round convention, not a measured constant. Sensitivity is not flat across the band: the ear responds most readily to mid frequencies and requires considerably more level at the extremes for a tone to be detected at all. Individual range varies, and hearing sensitivity changes over a lifetime. The WHO fact sheet on deafness and hearing loss describes the main causes of hearing loss, including aging and noise exposure, and the scale of it worldwide. This page describes terminology only; questions about your own hearing belong with a qualified clinician.

Audible versus measurable

Microphones and analyzers detect energy well outside the audible band. "Audible" is a statement about human perception, not about whether a signal exists. That distinction shows up in spec sheets: a frequency response figure describes what a device reproduces, not what a listener hears. A speaker rated down to 25 Hz still depends on room, level, and listener for any of that output to register.

For levels, the same split applies. Decibel figures are ratios against a stated reference, and a number alone says nothing about audibility until you know the reference and the frequency. See what a decibel actually measures for the reference part.

Why the audible band decides sample rate

Digital audio samples a waveform at a fixed rate. The sampling theorem sets the rule: to represent a band-limited signal without aliasing, the sampling rate must be greater than twice the highest frequency present. Stanford CCRMA's treatment of the sampling theorem gives the formal statement; the federal digitization guidelines summarize the same Nyquist–Shannon basis in their definition of audio sampling rate.

Apply it to the conventional band. Half of 44,100 Hz is 22,050 Hz. Half of 48,000 Hz is 24,000 Hz. Both sit above 20 kHz, which is why consumer and production rates cluster where they do: the ceiling of the audible band is the design constraint, plus headroom for the anti-alias filter to roll off.

That is also why higher rates are argued about rather than assumed. Going to 96 kHz moves the Nyquist limit to 48 kHz — far above the band anyone hears — so the case for it rests on filter behavior and processing headroom, not on capturing audible content that 44.1 kHz misses.

Where to look next

• What 44.1 kHz and 16-bit actually mean — the two numbers and what each controls.
• 44.1 kHz vs. 48 kHz — why two standard rates exist side by side.
• What do headphone impedance and sensitivity specs mean? — the level half of the same question, at the transducer.