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Sound is a form of energy that propagates as mechanical vibration or waves through a medium such as air, water or solids. Sound waves can be reflected, refracted and diffracted and have frequency, wavelength and amplitude.
There are three types of sound waves and they are; longitudinal, transverse and surface sound waves.
Longitudinal waves are characterized by particles vibrating parallel to the wave direction. Examples are sound waves in air, solid and water.
Transverse waves are characterized by particles vibrating perpendicular to the wave direction. Examples are light waves, string vibrations etc.
Surface waves travel along the surface between media such as air or water. Examples are ocean waves, Rayleigh waves (earth quakes etc.).
Sound waves are characterized by the following physical phenomenon; frequency, wavelength, amplitude, speed, period and phase. Where the;
Frequency is the number of oscillations per second (Hz).
Wavelength is the distance between consecutive compressions in millimeters(mm).
Amplitude is the maximum displacement from equilibrium in millimeter and it is related to loudness.
Speed is the speed of propagation of the sound waves through a medium in metres per second depending on the medium.
Period is the time for one oscillation of the sound wave in seconds.
Phase is the position in the wave cycle in radians or degrees.
Also sound waves can be described in terms of its frequencies such as infrasound, audible sound, ultrasound and hyper sound.
Infrasound has frequencies less than 20Hz and they are exhibited as subsonic earthquakes, animal communications etc.
Audible sounds have frequencies within the range of 20Hz to 20KHz which is within the human hearing range.
Ultrasounds have frequencies greater than 20KHz and are used as ultrasound for medical imaging, cleaning etc.
While hyper sounds have frequencies greater than 1GHz and are useful for research and industrial applications.
The advantages of sound are as follows; sound enables human communication and language. Sound allows for non-invasive medical imaging which is safer than X-ray. Sound enables music, art and emotional expression. Sonar and echolocation allows navigation in complete darkness or murky water.
Sound based alarms and alerts are highly effective regardless of lighting conditions. Acoustic monitoring can detect structural faults in buildings, pipelines and aircrafts without dismantling them. Sound therapy has demonstrated benefits of stress, sleep, pain management and cognitive focus.
The disadvantages of sound are as follows; excessive noise cause hearing loss, cardiovascular stress, sleep disruption and reduce cognitive performance. Sound waves travels relatively slowly compared to light limiting some real-time applications. It requires a physical medium making it useless in a vacuum. Low frequency sound from industrial sources can cause nausea, anxiety and disorientation in humans. Acoustic eavesdropping possesses security risks. Sonic booms from supersonic aircrafts cause property damage and psychological distress.
Sound finds widespread applications in the following; ultrasound imaging, tumor destruction, breaking of kidney stones, hearing and cochlear implants. Sonar for submarine detection, acoustic landmine detection, long range acoustic devices for crowd control and underwater communication, communication and mobile network. They are also used in the industry for ultrasonic cleaning of delicate components, nondestructive testing (NDT) of welds and materials, flow measurements in pipelines and level sensing tanks and so on.
The future of sound will depend on the advances and development in the following technologies; spatial and immersive audio. Technologies like Dolby Atmos, apple spatial audio and ambisonics are making 3d soundscape main stream in gaming, VR/AR and streaming. AI generated sound and voice is transforming media. AI can now clone voices with minimal samples, generate realistic soundscapes, compose music and restore degraded audio recordings. Ultrasound therapeutics will become a major medical frontier. Focused ultrasound can potentially open the blood-brain barrier for targeted drug delivery, treat Parkinson tremors and ablate tumors non-invasively and son on.
SOURCES:
- The physics of sound by Richard E. Berg and David G. Stork.
- The science of sound by Thomas D. Rossing, Richard F. Moore and Paul A. Wheeler.
- Sound: A very short introduction by Mike Goldsmith.
- Music, physics and engineering by Harry F. Olsen.
- Acoustics: An introduction to its physical principles and application by Allan D. Pierce.
