Acoustics and its Fundamental Concepts

About the Study

Acoustics is a branch of physics that studies mechanical waves in gases, liquids, and solids, including vibration, sound, ultrasound, and infrared. An acoustician is a scientist who works in the field of acoustics, whereas an acoustical engineer works in the field of acoustics technology. Acoustics is used in almost every aspect of modern society, the most obvious being the audio and noise control industries. Hearing is one of the most important aspects of animal survival, and speech is one of the most distinguishing features of human development and culture. As a result, acoustics is used in many aspects of human society, including music, medicine, architecture, industrial production, warfare, and others. Similarly, animal species such as songbirds and frogs use sound and hearing to aid in mating rituals or to mark territories. As in many other fields of knowledge, art, craft, science, and technology have stimulated one another to advance the whole. The "Wheel of Acoustics" by Robert Bruce Lindsay is a well-known overview of the various fields of acoustics.

Fundamental concepts

Wave propagation-pressure levels: Sound waves propagate as disturbances in the ambient pressure level in fluids such as air and water. While this disturbance is usually minor, it is audible to the human ear. The smallest sound a person can hear, known as the hearing threshold, is nine orders of magnitude lower than the ambient pressure. The loudness of these disturbances is proportional to the Sound Pressure Level (SPL), which is measured in decibels on a logarithmic scale.

Wave propagation-frequency: Sound pressure levels are often discussed in terms of frequencies by physicists and acoustic engineers, in part because this is how our ears interpret sound. Pressure vibrations with a higher or lower number of cycles per second are what we perceive as "higher pitched" or "lower pitched" sounds. Acoustic signals are sampled in time and then presented in more meaningful forms such as octave bands or time frequency plots in a common acoustic measurement technique. Both of these well-known techniques are used to analyses sound and gain a better understanding of the acoustic phenomenon. The electromagnetic spectrum is divided into three parts: audio, ultrasonic, and infrared. The audio frequency range is 20 Hz to 20,000 Hz. This range is significant because the human ear can detect its frequencies. Speech communication and music are two applications for this range. The ultrasonic range refers to frequencies of 20,000 Hz and higher. Shorter wavelengths in this range allow for higher resolution in imaging technologies. Ultrasonic frequency range is used in medical applications such as ultrasonography and elastography. The lowest frequencies on the spectrum are known as the infrasonic range. These frequencies have the potential to be used to investigate geological phenomena such as earthquakes.

Analytical instruments such as the spectrum analyzer make it possible to visualize and measure acoustic signals and their properties. A spectrogram produced by such an instrument is a graphical representation of the time-varying pressure level and frequency profiles that define a specific acoustic signal.

Transduction in acoustics

A transducer is a device that transforms one type of energy into another. This means converting sound energy into electrical energy in an electroacoustic context (or vice versa). Loudspeakers, microphones, particle velocity sensors, hydrophones, and sonar projectors are examples of electroacoustic transducers. These devices transform a sound wave into or out of an electric signal. Electromagnetism, electrostatics, and piezoelectricity are the most commonly used transduction principles.

Most common loudspeaker transducers (e.g., woofers and tweeters) are electromagnetic devices that generate waves by driving a suspended diaphragm with an electromagnetic voice coil, sending off pressure waves. Electret and condenser microphones use electrostatics, which means that when a sound wave strikes the microphone's diaphragm, it moves and causes a voltage change. Piezoelectric transducers are used in medical ultrasonography ultrasonic systems. These are made of special ceramics in which mechanical vibrations and electrical fields are linked by a material property.