In this section, we will learn about range, or pitch extent.

　 Range of Sound

Sound within the range audible to the human ear is called “audible sound,” which is said to be ranged around 20Hz-20kHz. ※20kHz=20000Hz However, the range of audible sound differs from person to person and it tends to become smaller as a person gets older. If you refer to the graphs below, you will see that the high pitch is difficult to hear for elder persons. So a very high-pitched sound like mosquito tone can be heard only by young people. We will explain about this later. ※mosquito tone is ranged around 17,000 Hz.



Sound waves of 100Hz or less in frequency are called “infrasonic (low-frequency sound waves).” Those of less than 20Hz, which is inaudible to the human ear, are called “ultra-low-frequency sound waves,” those of more than 20kHz are “ultrasonic.” Please refer to the next chart.

Let's listen to the actual sound, from low-pitch to high-pitch.


By what kind of movie could you listen up to Hz? I think that it is difficult to hear the sound beyond 10000 Hz when you get older. So why will not it be hard to listen to treble as you age. Let's start with the mechanism by which humans recognize sound.

　 Mechanism of how human ears catch

　　and recognize sound


※出典　補聴器と難聴の総合情報サイト　「みみから。」　(http://www.widexjp.co.jp/deafness/what/symptoms.html)より引用

Please refer to the structure of the human ear above. It is divided into three areas: external, middle, and inner. External and middle areas pass the sound from the outside to the inner one. In the inner area, when the sound arrives at the basement membrane inside the spiral-shaped cochlea, it recognizes the frequencies and transforms the sound into nerve impulses that travel to the brain. The front-side cells of basement membrane recognize high-frequency/high-pitch sound while the inner-side cells recognize low-frequency/low-pitch sound.
As people get older, their ears, especially the front-side cells of basement membrane, have been exposed to more and more sounds and their function to recognize high-frequency/high-pitch sound inevitably decrease. This is why elder people tend to have difficulty in hearing high-pitch sound.

　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　↑Phenomena of Sound