PRESENTATION ON ARCHITECTURAL ACOUSTICS

SUBMITTED TO;RAVI SIR

SUBMITTED BY;RIYAS.MS13061AA0046TH SEMSARCA

UNIT- 2--------SOUND

INTRODUCTION SOUND

Sound is a vibration that propagates as a typically audible mechanical wave of pressure and displacement, through a medium such as air or water. In physiology and psychology, sound is the reception of such waves and their perception by the brain.

Generation

sound is generated when an object vibrates, causing the

adjacent air to move, resulting in a series of pressure waves

radiating out from the moving object. For example, when a violin string vibrates upon

being bowed or plucked, its movement in one direction pushes the molecules of the air before it, crowding them together in its path. When it moves back again past its original position and on to the other side, it leaves behind it a nearly empty space,

PROPOGATION OF SOUND.

Sound moving through a media via a sound wave. The media can be anything air , water and even plasma. The speed of sound is determined by the properties of the media, and not by the frequency or amplitude of the sound. Sound waves, as well as most other types of waves, can be described in terms of the following basic wave phenomena.

RECEPTION OF SOUND

A drum produces sound via a vibrating membrane. In physics, sound is a vibration that propagates as a typically audible mechanical wave of pressure and displacement, through a medium such as air or water. In physiology and psychology, sound is the reception of such waves and their perception by the brain.

Frequency is the measurement of the number of times that a repeated event occurs per unit of time. The frequency of wave-like patterns including sound, electromagnetic waves (such as radio or light), electrical signals, or other waves, expresses the number of cycles of the repetitive waveform per second.

FREQUENCY OF SOUND

Distance between successive compressions or rarefactions.Compressions:Areas in the wave where the air molecules are pushed close together and so at a slightly higher pressure.Rarefaction:Areas in the wave where the air molecules are further apart and so at a slightly lower pressure.

WAVE LENGTH OF SOUND

VELOCITYOF SOUNDThe velocity of sound, or of acoustic traveling waves, is a physical constant for any given medium at a specific pressure and temperature. In dry air at sea level at 0 degrees Celsius , the speed of sound is approximately 331.4 meter s per second (m/s). Temperature, pressure, and humidity affect this value to some extent.In most liquids and solids, the speed of sound is greater than in air at sea level. In part, this is because traveling waves in air occur because of compression, but traveling waves in solids and liquids occur because of lateral motion of the molecules, a phenomenon that generally propagates faster.

SOUND intensity is defined as the sound power per unit area. The SI unit of sound intensity is the watt per square meter (W/m2). The usual context is the noise measurement of sound intensity in the air at a listener's location as a sound energy quantity

INTENSITYOF SOUND

INVERSE SQUARE LAW OF SOUND

Sound from a point source obeys the inverse square law. It's intensity in decibels can be calculated by comparing the intensity to the threshold of hearing. At a distance r = m = ft. from a point source of acoustic power P = watts. the sound intensity is x10^ watts/m2= dB

 Inverse-square law is  stating that a specified physical quantity or intensity is inversely proportion to the square of the distance from the source of that physical quantity. The fundamental cause for this can be understood as geometric dilution corresponding to point-source radiation into three-dimensional space.

DECIBELA unit used to measure the intensity of a sound or the power level of an electrical signal by comparing it with a given level on a logarithmic scale. The decibel (dB) is a logarithmic unit used to express the ratio of two values of a physical quantity, often power or intensity. One of these values is often a standard reference value, in which case the decibel is used to express the level of the other value relative to this reference. The number of decibels is ten times the logarithm to base 10 of the ratio of two power quantities, or of the ratio of the squares of two field amplitude quantities. One decibel is one tenth of one bell, named in honor of Alexander Graham Bell; however, the bell is seldom used.

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