[BU3] BUILDING UTILITIES 3_MODULE 2,3&4

Transverse Waves

Cause the medium to move perpendicular to the direction of the wave

Longitudinal Waves

Cause the medium to move parallel to the direction of the wave

Longitudinal Waves

Acts in one dimension

Transverse Wave

Acts in two dimensions

Longitudinal Wave

The wave cannot be polarized or aligned

Transverse Wave

The wave can be polarized or aligned

Longitudinal Wave

The wave can be produced regardless of the medium [gas, liquid, and sound]

Transverse Wave

The wave can only be produced in solid and on the surface of a liquid

Longitudinal Wave

It consists of rarefactions and compressions

Transverse Wave

It is made of troughs and crests

Velocity (v) = Frequency (f) x Wavelength (λ)

Formula of Wavelength

Velocity

The distance of a wave travels per second

m/s

SI unit of velocity

Frequency

The number of crests [peaks] or troughs that pass a point per second; the number of complete waves generated per second

Hz (hertz)

SI unit of frequency

Wavelength

The distance between two successive crests or two successive troughs in a wave

m (metre)

SI unit of wavelength and amplitude

Amplitude

The magnitude of a maximum displacement from the rest position (or equilibrium) of the wave. This is based on the height of the crest or depth of trough from the rest position

Wavefront

Is defined as an imaginary line that connects all the crests (or points in phase) on a wave. It can be represented by straight lines, concentric centres, and other shapes

Speed of Sound

Varies greatly depending upon the medium it is traveling through

Speed of Sound

Is determined by a combination of the medium's rigidity (or compressibility in gases) and its density

Speed of Sound

More rigid (or less compressible) the medium, the faster the speed of sound

Speed of Sound

The greater the density of a medium, the slower the speed of sound

Sound of Speed

The speed of sound in air is low, because air is compressible

v=fλ

In a given medium under fixed temperature and humidity, v is constant therefore the relationship between f and λ is inverse

v=fλ

The higher the frequency, the shorter the wavelength of a sound wave

Sound Propagation

The basic parameters of this model related to the perception of loudness of loudness are SL, TL, NL, SNR, RL, and DT

RL=SL-TL

Simple definition of Sound Propagation

Sound Intensity

Quantity for describing the loudness of sounds

Intensity of a wave

Is the power per unit area carried by the wave

Power

Is the rate at which energy is transferred by the wave

W/m^2

SI unit for intensity

I=P/A

In equation form where P is the power through an area A

Free Field

Condition of sound that occurs outdoor in an open field with no sound reflections

Free Field

Sound level drops 6dB for every doubling of distance for sound traveling spherically

Free Field

Occur when sound waves are free from influence of reflective surfaces under the free field conditions, sound energy from the point sources spreads spherically and drops of 6db for each doubling of distance from the source

Reveberant Field

Indoors sound energy drops off free field conditions only near the source because room surfaces reflect sound

Decibel Scale

Measures loudness of sound

Sound Intensity Level (SIL)

Also called acoustic intensity level, is the absolute logarithmic unit of the sound intensity relative to a reference value of 10^-12 W/m^2

Inverse Square Law

The sound intensity is inversely proportional to the square of its distance traveled

Sound Intensity Level and Sound Pressure Level

To which most mammals are sensitive extend over many orders of magnitude and, for this reason, it is convenient to use a logarithmic scale when measuring sound.