Question

Infrasonic sound is of frequency:

Answer 1

In this question we will see the basics of sound and audible frequency range. This will help us to get our required result for the question. Further, we will also discuss the basics of a supersonic sound and its frequency range, for our better understanding.

Complete solution:
As we know, from the basic definition of sound that a sound is produced when some particles or object vibrates.
Now, the human audible frequency range is from 20Hz to-20kHz. Below and above this range humans cannot hear the sound clearly. This is also called audible range. Infra-sound is a low-frequency sound.
Now, we know that the infrasonic sound is defined as the sound that is lower in frequency than 20 Hz or we can say, cycles per second, the normal limit of human hearing. So, we can say that our hearing becomes less sensitive as the frequency decreases below this frequency range. For humans to perceive infrasound, the sound frequency must be sufficiently high.

Therefore, we get the required answer i.e., the infrasonic sound is of frequency below 20Hz.

Additional information:
We know that the supersonic speed is the speed of an object that exceeds the speed of sound. In an object which is traveling in dry air at a temperature of 20 °C or 68 °F at sea level, this speed is approximately 343.2 m/s. Further, speed that is greater than five times the speed of sound is referred to as hypersonic.
Further we can also understand this concept by observing the vehicles that are flying at supersonic speeds are flying faster than the speed of sound. We know that the speed of sound is about 768 miles per hour or we can say, 1236 kilometers per hour, at sea level. These speeds are called the Mach numbers. The Mach number is defined as the ratio of the speed of the aircraft to the speed of the sound.

Note:
Here we should notice that the speed of sound is different in different mediums. Further, the speed that is measured as more than the speed of sound is termed differently, for example- supersonic, hypersonic etc. We should also note that the speed of sound cannot be the same or more than the speed of light.