Sound happens when something vibrates and creates a pressure wave. Then particles in the surrounding medium (air, water, or solid) are also caused to vibrate.
As these particles vibrate, nearby particles also vibrate, and the sound is transmitted further through the medium. The human ear recognizes a sound wave when the wave particles vibrate small sections of the inner ear.
Sound is measured in decibels (dBs) and frequency (Hertz or Hz)
What Is a Decibel?
A sound can range from low to high. A decibel (dB) is the term used to describe a sound’s intensity or pressure. Normal human hearing range is between 0 to 140 dBs.
Most human speech sounds range between 30 to 70 dBs. However, our ability to hear the highest frequencies is reduced the older we get. Also, hearing damage due to exposure to excessive noise levels or injury affects how well we can hear.
What Decibel Range Constitutes Hearing Loss?
People struggling to hear sounds between 30 to 40 dBs are said to have mild hearing loss. People who have hearing difficulties in the 50 to 70 dB range have moderate hearing loss.
What Decibel Range Can Cause Hearing Damage?
It’s best to avoid prolonged exposure to sounds above 80 dBs because that noise level can damage hearing. Examples include ambulance sirens, power tools, and fireworks.
What Is Sound Frequency?
Hertz (Hz) is the term used to describe the frequency or pitch of a sound. The sounds people process every day range from 250 to 6,000 Hz. However, people with good hearing can hear and process sounds between 20 and 20 kHz (20,000 Hz). As we age, we begin to lose our ability to hear high-frequency sounds.
- Examples of low-frequency sound: barking dogs; certain speech sounds, e.g., the letters j, u, and z; lawnmowers; thunder.
- Examples of high-frequency sound: chirping birds; women’s and children’s voices; certain speech sounds, e.g., the letters f, s, and th; rainfall.
All Sound Frequencies Are Not Heard Equally
In the mid-frequency band (between 500 Hz and 5 kHz), sounds at sound pressure levels of around 0 dB are audible to young, healthy ears. At lower and higher frequencies, sounds must be louder to be audible.
- Example: A sound pressure level of 40 dBs is necessary for sound to be audible at 50 Hz.
At much higher sound pressure levels (around 120 dBs), sound is felt more so than heard. This level constitutes the threshold of feeling.
At even higher levels (say 140 dBs), the “feeling” becomes quite uncomfortable, and the threshold of pain is reached.
How High Can You Actually Hear?
Find out what is the highest frequency you can pick up. Click on this video and stop as soon as you can no longer hear anything. Note that the technology you’re using might impact what you’re hearing, so this experiment might not be entirely accurate. However, minus a hearing impairment, most people can hear up to around 8,000 Hz.
How Well Do We Hear Compared to Animals?
The answer is, not very! For example, the range for dogs is 40 Hz to 60 kHz. The hearing range for bats, that need sensitive hearing to compensate for lack of visual stimuli, is between 9 kHz and 120 kHz. Even mice do better – they communicate using high-frequency sounds, some of which are inaudible to humans.