atom03:Sound
Contents |
what is sound
Sound is a mechanical disturbance of medium. Sound waves are longitudinal waves, waves which propagate via a series of compressions and rarefactions in a medium - usually air.
sound vs noise
Sound is a form of energy that is transmitted by pressure variations which the human ear can detect. When one plays a musical instrument, say a guitar, the vibrating chords set air particles into vibration and generate pressure waves in the air. A person nearby may then hear the sound of the guitar when the pressure waves are perceived by the ear. Sound can also travel through other media, such as water or steel.Apart from musical instruments, sound can be produced by many other sources - man's vocal cord, a running engine, a vibrating loudspeaker diaphragm, an operating machine tool, and so on. Noise is unwanted sound. Usually the sound of a violin is referred to as music - is something pleasing. Depending on other factors, the sound may be perceived as noise.Noise perception is subjective. Factors such as the magnitude, characteristics, duration, and time of occurrence may affect one's subjective impression of the noise.
sound glossary
Absorption The tendency of sound waves to be soaked up by soft surfaces.
Amplitude The strength of sound waves or an electrical signal;determines loudness.
Amplifier Increases the amplitude of a signal.
Attenuate To make weaker.
Conductor element that allows the free transmission of sound.
dB (Decibel) A relative unit of measure between two sound or audio signal levels. A difference 1 dB is considered to be the smallest that can be detected by the human ear.
Dispersion The area throughout which the sound produced is distributed.
Distortion The alteration of the original shape (or other characteristic) of a sound waveform.
Dynamic Range The difference between the softest and loudest extremes within an audio signal.
Efficiency The ratio of a device's energy output to its energy intake.
Filter A device that removes unwanted frequencies or noise from a signal.
Frequency The number of sound waves that pass a given point in one second. The determiner of pitch.
Inductance A circuit's opposition to a change in current flow.
Omnidirectional Capable of picking-up sound or radiating sound equally from all directions
Phase The relationship of an audio signal or sound wave to a specific time reference.
Pitch The quality of a sound governed by the rate of vibrations producing it; the degree of highness or lowness of a tone.
Sound Level Meter A device that measures, in dB, the amplitude of sound waves.
Sound Reinforcement The use of electronic devices to reinforce, alter or increase the level of sound.
Tone Sound that can recognized by its regularity of vibration.
Unidirectional Picking up sound primarily from one direction.
Vibration The analogous motion of particles of mass the analogous motion of the particles of a mass of air, whose state of equilibrium has been disturbed, causing the transmission of sound.
human perception and reaction to sound
text / diagrams / annoyance - related to noisiness (absolute /relative)
spaces physical noise characterization
geometries / ground attenuation / fixed sources....
sources: environmental protection department - goverment of Hong Kong / Long, Architectural Accoustics. Elsevier Academic Press, London 2006.
