Question

Why are ultrasonic waves not audible to humans?

Short answer

Ultrasonic waves are not audible to humans because their frequency is higher than 20,000 Hz, which is beyond the human hearing range.

Step-by-step solution

Understand the Frequency Range of Human Hearing

The audible range for human hearing typically falls between 20 Hz and 20,000 Hz (20 kHz). This means that any sound with a frequency within this range can be heard by most humans.

Define Ultrasonic Waves

Ultrasonic waves are sound waves that have a frequency higher than 20,000 Hz. These waves are beyond the upper limit of the human hearing range.

Compare Frequencies

Since ultrasonic waves have a frequency greater than 20 kHz, they are outside the audible range for humans.

Conclude Why Ultrasonic Waves Are Not Audible

Ultrasonic waves exceed the frequency range that the human ear can detect. Thus, they cannot be heard by humans.

Key concepts

Frequency Range of Human Hearing

The human ear is an incredible organ capable of detecting a wide range of sounds. The typical frequency range that most humans can hear falls between 20 Hertz (Hz) and 20,000 Hertz (20 kHz). Within this range, we can discern a variety of pitches, from the deep rumble of a bass drum to the high-pitched whine of a tea kettle.

As we age, the upper limit of this range often decreases. Many adults may not be able to hear sounds close to 20 kHz. Knowing the frequency range of human hearing is essential for understanding what sounds we can and cannot perceive.

Ultrasonic Waves

Ultrasonic waves are a type of sound wave that exists above the frequency range audible to humans. Specifically, they have frequencies higher than 20,000 Hz (20 kHz). Because these waves are beyond our hearing capabilities, they are termed 'ultrasonic', meaning 'beyond sound'.

Ultrasonic waves have many practical applications. For example, they are used in medical imaging (like ultrasounds), industrial cleaning, and even in dog whistles. Even though we cannot hear these waves, they can still interact with matter and have useful properties.

Audibility Limits

The audibility limits of human hearing refer to the boundaries within which we can detect sound frequencies. For most humans, this range is between 20 Hz and 20 kHz. Sounds below 20 Hz are considered infrasonic, while sounds above 20 kHz are ultrasonic.

These limits vary between individuals due to factors like age, ear health, and genetic differences. For example, younger people often have a broader hearing range compared to older individuals. Understanding these limits helps us comprehend why certain sounds, like ultrasonic waves, fall outside our capability to hear.

Sound Frequency

Sound frequency is the number of vibrations or cycles per second of a sound wave, measured in Hertz (Hz). Lower frequencies (e.g., 100 Hz) produce deeper, bass-like sounds, while higher frequencies (e.g., 10,000 Hz or 10 kHz) produce sharper, treble sounds.

Higher frequencies vibrate more rapidly and can travel shorter distances. Lower frequencies, however, can travel longer distances and penetrate through obstacles better. Understanding sound frequency is critical to grasping why we can hear certain sounds within the 20 Hz to 20,000 Hz range and why ultrasonic waves are inaudible.