Speech Perception

Human Hearing Test

The ear is an amazing body part because it enables humans and animals to hear what goes on around them. Hearing is one of the five senses of the body. The ears are like antennas that help the body to pick up sound waves and vibrations. Sound travels in waves through the air, the ground, and various other substances. Sound cannot be seen, but it can be felt by vibrations. The full range of human hearing is 20 Hz to 20 kHz (Caldarelli, David D. and Ruth S. Campanella. Ear. World Book Online Americas Edition. 26 May 2003). The range of frequencies that an individual can hear deteriorates with age and with exposure to unsafe volume levels.

Human Hearing Test Equal by Loudness Contours

The standard method to measure human hearing sensitivity involves finding the Equal Loudness Contours of the human ear
What are the Equal Loudness Contours? Basically, they are curves that are the inverse of frequency response curves, so that they are literally curves of equal loudness. When Fletcher and Munson did the first ones (in 1933), they started with 1 kHz. at some known sound pressure level as a reference, and measured all other audible frequencies in comparison to 1 kHz., determining at what sound pressure level each frequency sounded as equally louder as 1 kHz. The resulting curve is known as an equal loudness curve, shown in the following picture.

This graph, courtesy of Lindosland, shows the 2003 data from the International Standards Organisation for curves of equal loudness determined experimentally. Plots of equal loudness as a function of frequency are often generically called Fletcher-Munson curves after the original work by Fletcher, H. and Munson, W.A. (1933) J.Acoust.Soc.Am. 6:59.

One of the simplest human hearing test is performed by playing pure sine wave tones in front of a listener. You can test your hearing capability by playing this interesting video.

What does your hearing test mean?

Most people will find that their hearing is most sensitive around 1–4 kHz and that it is less sensitive at high and low frequencies. Children usually hear 16 kHz moderately well. The high frequency hearing of adults depends on age and exposure to loud sounds. It is not uncommon for adults to have very low sensitivity for the highest frequencies. (Your children may respond to that 16 kHz tone that you cannot hear.) If you cannot hear the lowest frequencies, it’s probably because you are using loudspeakers. For more accurate results you need headphones that enclose your ears for this.

The human ear has the capability of hearing many of the sounds produced in nature, but certainly not all. Some low frequencies like a heart beat of 1 or 2 Hz can not be heard, just like sonar sounds produced by dolphins which are too high. Any frequency that is below the human range is known as infrasound. It is so low that it may be detected by a creature with big ears, such as an Elephant. In fact, recent research indicates that elephants also communicate with infrasound. Ultrasound, on the other hand, is above the range of the human ear. Bats, whales, porpoises, and dolphins use ultrasound for navigation. Most bats can detect frequencies as high as 100,000 Hz!