SOUND is vibration in an elastic medium. In our daily life, we hear so many sounds around us like chirping birds, barking dogs, honking vehicles on the street etc. all these are of so many types, tones and levels. In fact, we can also recognize a person by just his or her voice. Sound therefore plays a very important role in our life. But what is SOUND ?
Sound is a result of vibration, this vibration is produced by a source and then it travels in a medium as a WAVE and is ultimately sensed through the ear - drum.
Sound is also a form of energy, just like electricity, heat or light. In physics, sound is a vibration that typically propagates as an audible WAVE of pressure, through a transmission medium such as a gas, liquid or solid.
Sound is made up of three very basic elements:
- Frequency: how fast the vibrations are occurring
- Intensity: how loud the sound is
- Timbre: the sound's quality
The human ear has a frequency hearing range from 20 to 20,000 Hz. A sound's intensity corresponds to the amount of energy associated with that sound. The decibel (dB) is used for measuring the sound's energy in a way in which we humans perceive loudness. Timbre is the complex wave pattern that occurs when overtones (multiples of the fundamental frequency) are present along with the fundamental frequency.
Sound is a longitudinal, mechanical wave. Sound can travel through any medium, but it cannot travel through a vacuum. Sound is a variation in pressure. A region of increased pressure on a sound wave is called compression (or condensation). A region of decreased pressure on a sound wave is called rarefaction (or dilation).
Waveform Characteristics:
- Amplitude: How loud the signal is:
This can also be considered as “intensity”. Amplitude is simply volume i.e how loud or soft the sound is.. The unit of measurement for amplitude is called the “Decibel”, written as “Db”.
- Frequency: How often it’s repeated
Frequency is the rate at which a sound wave completes a cycle of peak, trough and back to peak. PITCH from the subjective domain is termed as Frequency in the objective domain.
A major part of recording, mixing, and mastering involves assembling, shaping and refining different frequency ranges. We measure sound frequency in terms of “cycles per second”, or “Hertz”.
- Velocity: The speed of the Waveform. Simply put the speed at which sound travels.
- Wave Length: Start to the finish of the sound.
- The distance between successive crests or troughs of a sound wave. The wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeat. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, troughs or zero crossings.
- Envelope: Smooth curve that outlines the extremities in Amplitude. Envelope is also referred to as an ADSR. This is because Envelope is really 4 separate characteristics in one.
- Attack is how quickly a sound reaches it’s peak volume after the sound is activated (the key is pressed).
- Decay is how quickly the sound drops to the sustain level after the sound hits it’s peak.
- Sustain The constant volume that a sound sits at after decay until the note is released. So long as you are still holding the key down, and the sound has already passed through it’s attack and decay phases, then it will sit at this volume until you release the key.
- Release How quickly the sound fades to nothing once a note ends (the key is released). Some sounds might end instantly after a key is released, others might ring out longer.
OTHER THAN THE ABOVE DISCUSSED THERE ARE A FEW MORE PROPERTIES :
- Reflection – Sound waves like light are reflected from the surfaces obeying laws of reflection, angle of incident is equal to the angle of reflection.
- Refraction - sound waves bend when the parts of the wave-front travel at different speeds. This for sound generally occurs in uneven winds or when sound is travelling through an air of uneven temperatures.
- Deflection - when two frequencies and amplitude overlap it produces interference of the waves. It is a characteristic of all wave motion whether sound, light or water.
- Interference - Spreading of waves around the corner of obstacles or apertures. Due to diffraction of sound through the doors and windows of a space sound is heard inside the room from the outside.