Audible sound

Professional Definition

In physical and psychoacoustic terms, this concept is defined as follows:

Audible sound is elastic waves that propagate through a material medium (usually air), with a frequency range of about 16 Hz to 20,000 Hz (20 kHz). This range is capable of stimulating the Corti organ in the human inner ear and creating an auditory sensation.

It is important to note that these limits are conventional and individually variable. The lower limit (infrasonic) is fluid, as with sufficiently high acoustic pressure we can "feel" vibrations lower than 16 Hz throughout our body. The upper limit (ultrasonic) drastically decreases with age in a process called presbyacusis – an average adult rarely hears sounds above 15-16 kHz.

Acoustics in Simple Words

Imagine a piano keyboard stretching infinitely in both directions. Audible sound is just a small slice of keys in the middle, which, when pressed, produce a tone audible to your ear. All the keys to the left (very slow vibrations) and to the right (very fast vibrations) still move the strings and set the air in motion, but to you, they remain silent.

Another good analogy is the spectrum of light. Just as our eyes see only "visible light" (the rainbow) and do not see infrared or ultraviolet, our ears are tuned only to a specific range of frequencies. What is silence to us may be a clear acoustic signal to a bat or a dog.

Summary

Audible sound is a subjective window into the acoustic world, limited by the physiology of the human ear. Although acoustical waves can physically have any frequency, for acoustic engineering and hearing protection, the key range is 20 Hz – 20 kHz, which encompasses all our verbal communication and musical perception.