Elephants can communicate using very low frequency sounds, with pitches below the range of human hearing. These low frequency sounds$($frequency less than $20\ Hz),$ termed infrasonic sounds, can travel several kilometers, and provide elephants with a private communication channel that plays an important role in elephants complex social life. Their frequencies are as low as the lowest notes of a pipe organ.
For transverse wave, cohesion is an important property in the medium through which the wave energy can be transported. Gas does not have such a cohesion property. Hence there is no chance for transverse waves to be propagated through gas medium. So the sound propagates in a gaseous medium by longitudinal wave.
The Jal Tarang is a melodic percussion instrument that originates from the Indian subcontinent. It consists of a set of ceramic or metal bowls filled with water. The bowls are played by striking the edge with beaters, one in each hand.
Adult humans can hear from $20\ Hz$ to $20000\ Hz$ of frequency. Sound with frequency lower than $20\ Hz$ are called infrasonic, and higher than $20000\ Hz$ are called ultrasonic or supersonic which are inaudible to humans.
Infra-sound is a low-frequency sound. It is sound that is lower in frequency than $20\ Hz$ or cycles per second, the normal limit of human hearing. Hearing becomes gradually less sensitive as frequency decreases, so for humans to perceive infrasound, the sound pressure must be sufficiently high. The ear is the primary organ for sensing infra-sound, but at higher intensities it is possible to feel infra-sound vibrations in various parts of the body.
$SONAR -$ Sound navigation and ranging is a technique, that uses ultrasonic sound waves to navigate and to detect objects on or under the surface of water.
Time taken to complete one vibration is called is called time period $(T).$
Thick strings with large diameters vibrate slower and have lower frequencies than thin ones. That is, lower the pitch. A thin string with a $10$ millimeter diameter will have a frequency twice as high as one with a larger, $20$ millimeter diameter. This means that the thin string will sound one octave above the thicker one. Hence, notes of different frequencies can be produced by vibrating different strings with different diameters.
The two most important properties of sound are amplitude and frequency because amplitude determines the loudness of sound and frequency determines its pitch. The loudness and pitch affect the quality of sound.
Sonar is a device that uses ultrasonic waves to measure the distance, direction and speed of underwater objects. Sonar consists of a transmitter and a detector and is installed in a boat or a ship.
The transmitter produces and transmits ultrasonic waves. The distance of the object that reflected the sound wave can be calculated by knowing the speed of sound in water and the time interval between transmission and reception of the ultrasound.
Because the tuning fork is in resonance with air column in the pipe closed at one end, the frequency is
$\text{n}=\frac{\big(2\text{N}-1\big)\text{v}}{4\text{l}}$ where $N = 1, 2, 3$
Sounds having frequency more than $20,000\ Hz$ are called Ultrasonic sound. As this is above the normal hearing range for humans, we cannot hear ultrasonic sound.
The persistence of sound in a hall is called reverberation.
Rhinoceros can produce infrasonic sound waves.
The depth of an ocean is estimated by a device, called $SONAR,$ which sends ultrasonic waves towards the bottom of ocean , and after reflection, waves come back to the sonar. The time is recorded between the emitting and the receiving waves and having the speed of waves in water , we get the depth of ocean.
The intensity of sound is an objective, measurable quantity. It does not depend on the response of our ears.
Loudness is a subjective quantity. It cannot be measured as a physical quantity.
The acronym $SONAR$ stands for SOund Navigation And Ranging. Sonar is a device that uses ultrasonic waves to measure the distance, direction and speed of underwater objects.