Building Utilities 3 AMACE REVIEWER (copy)

A vocabulary-focused flashcard set detailing technical acoustical terms, formulas, and physical phenomena from the Building Utilities 3 lecture notes.

Absorbing Materials

Materials that dissipate acoustic energy within their structure as heat and/or mechanical energy of vibration, often specifically designed for boundary surfaces of rooms or cavities.

Absorption

The ability of a material to absorb acoustical energy, measured in sabins; defined as the product of area ($s$) and the absorption coefficient ($\alpha$).

Absorption Coefficient (\alpha)

The fraction of sound energy impinging on a surface that is absorbed by that surface.

Acoustics

The science of sound, including its generation, transmission, and effects of sound waves, and the technology of designing spaces to meet hearing needs.

Acoustical Analysis

The detailed study of all pertinent sound sources, sound transmission paths and sound receptors in the context of particular acoustical problem.

Acoustical Environment

The overall environment, interior to exterior, that affects the acoustic condition of the space or structure under consideration.

Acoustical Impedance

The resistance to the flow of acoustical energy, measured in rayls at specific frequencies, which is affected by density and fiber diameter.

Acoustical Treatment

The use of acoustical absorbing or reflecting materials or sound-isolating structures to improve or modify the acoustical environment.

Airborne Sound

Sound that is transmitted through air by a series of oscillating pressure fluctuations.

Air Column

An air space enclosed on at least five sides which produces sound wave characteristics, such as pipes in a pipe organ.

Ambient

The existing surrounding conditions such as air or surface.

Amplification

Usually the increase in intensity level of an audible signal produced by means of loud speakers and associated electronic amplification apparatus.

Amplitude

The maximum displacement of the conductor molecules during each cycle of a sound wave.

Architectural Acoustics

The science and technology of controlling sound in and around buildings.

Attenuation

The lessening or reduction of sound level, for example from $80\,dB$ to $70\,dB$.

Background Sound

Noise from all sources in an environment, exclusive of a specific sound of interest.

Complex Tone

A sound sensation characterized by more than one frequency.

Compression

In sound, the concentration of the conductor molecules to produce a high-pitch layer of sound.

Conductor of Sound

A material that carries or transmits energy from one location to another; a sound conductor must be an elastic material.

Creep

Transmission of sound along curved surface.

Cycle

One complete displacement of a particle.

Cycles per second (CPS)

Unit of frequency.

Damping

Energy dissipation in an oscillating system that prevents a system from oscillating freely.

Decay Rate

The rate at which sound pressure level (in dB) decreases when the source of sound is eliminated.

Decibel (dB)

The basic metric unit for describing the magnitude of sound, calculated as $20$ times the logarithm to the base $10$ of the ratio of the sound pressure to a reference pressure of 0.0002 dyne cm^-2

Diaphragm

A thin body that separates two areas; in sound, the skin of a partition or ceiling which separates the room from the structural space in the center of the partition or ceiling assembly.

Diffuse Sound Field

A sound field in which the intensity of the sound is independent of its direction and sound energy flow is equal in all directions.

Direct Sound Field

A sound field in which the energy arrives at the receiver in a direct path from the source, without any contribution from reflections.

Distortion

Any change in the transmitted sound signal such that the sound received is not a faithful replica of the original source sound.

Echo

Sound waves which have been reflected back to a listener with sufficient magnitude and time delay.

Focusing

Concentration of reflected acoustic energy within a limited location in a room as the result of reflections from concave surfaces.

Free Field

A field free from boundaries that would otherwise tend to reflect sound.

Frequency

Number of complete oscillation cycles per unit of time. A unit of frequency often used is the hertz.

Fundamental Frequency

The lowest frequency present in a complex tone.

Flutter Echo

A rapid succession of echoes caused by reflection of sound back and forth between two parallel walls.

Geometric Acoustics

Behaviour of sound waves likened to that of light rays.

Harmonics

A component of sound containing more than one frequency which is an integral multiple of the lowest frequency.

Hearing

The subjective response to sound, including the entire mechanism of the external, middle and internal ear system and the nervous and cerebral operations that translate the physical stimuli into meaningful signals.

Hertz (Hz)

A measure of frequency equivalent to cycles per second (CPS)

Infrasound

Noise of a frequency less than 20 Hz, which is below the normal lower audible limit of the human ear.

Intensity (I)

The average rate of sound energy flow per unit area in a direction perpendicular to the area, expressed as I= P/A

Intensity Level (IL)

Ten times the logarithm of the ratio of sound intensity to a reference sound intensity.

Inverse Square Law

A principle stating that under free-field conditions, sound intensity varies inversely with the square of the distance from the source, expressed as $\frac{I_1}{I_2} = (\frac{d_2}{d_1})^2$.

Liquidborne Sound

Sound caused by pulsations of liquid pressure about the mean static pressure.

Loudness

The subjective attribute of an auditory sensation.

Masking

The obscuring or covering up of one sound by another.

Noise

Any unwanted sound. It is annoying and interferes with speech and hearing, or intense enough to cause hearing damage.

Noise Isolation Class (NIC)

A single number rating derived from Noise Reduction ($NR$) used to rate sound insulation.

Noise Reduction

The reduction in level of unwanted sound by any several means (e.g. distance in outdoor space, by boundary surface absorption, by isolating barriers of enclosures, etc.).

Octave

A frequency band whose upper limit is twice the lower limit.

Partials

Component of high frequencies.

Phon

A unit used to measure loudness level.

Pitch

The subjective attribute of an auditory sensation that enables sounds to be ordered on a scale from low to high frequency.

Pure Tone

A vibration produced at a single frequency, characterized by the period formula $T_p = \frac{1}{f}$.

Reflected Sound

The resultant sound energy returned from a surface(s) that is not absorbed or otherwise dissipated upon contact with the surface(s).

Resonance

A state in which the forces of oscillation of a system occur at or near a natural frequency of that system.

Reverberation

The persistence of sound in an enclosed space as a result of repeated reflection or scattering.

Reverberation Sound Field

Sound that is reflected from the boundaries of and furnishings within an enclosed space.

Reverberation Time

The time in seconds required for a sound level at a specific frequency to decrease $60\,dB$ after the source stops.

Sabin

The unit of measure of acoustical absorption equivalent to a square foot of perfectly absorptive material, named after Wallace Clement Sabine.

Sound

An oscillation in pressure of the atmosphere which is capable of being detected by the human ear.

Sound Absorbers

Materials that have the capacity to absorb sound, such as acoustical tile and panels, carpets, draperies and upholstered furniture.

Sound Absorption

The process of dissipating sound energy by converting it to heat. Sound absorption is the reciprocal of sound reflection.

Sound Attenuation

Lessening or reduction of sound, e.g. from 80 dB to 70 dB.

Sound Conditioning

Designing and equipping a space for effective retention of desirable sounds and maximum relief from undesirable acoustical effects.

Sound Diffraction

Acoustical phenomenon which causes sound waves to be bent or scattered around obstacles.

Sound Diffusion

When sound travels in all directions.

Sound Power

The rate at which acoustic energy is radiated. Usually measured in watts.

Sound Pressure

The fluctuation of pressure about atmospheric pressure. Usually measured in micropascals (μPa).

Sound Propagation

The origination of transmission of sound energy.

Sound Reflection

Reflection of sound energy.

Sound Reinforcement

Refers to the beneficial reinforcement of a sound signal provided by sound-reflecting surfaces or by a loudspeaker system.

Sound Insulation / Sound Isolation

The use of structures and materials designed to reduce the transmission of sound from one area to another.

Sound Transmission

The propagation of sound energy through various media.

Sound Transmission Class (STC)

A single number rating of the sound insulation value of a partition, door, or window.

Sound Absorption Coefficient (SAC)

The fraction of sound energy absorbed or otherwise reflected by a surface.

Sound Transmission Loss (STL)

The difference in decibels of the sound pressure level on the receiver side of a barrier compared to the source side.

Splay

A slight offset in angle (as little as $\frac{5}{8}\,in$ per foot) from a flat plane, used to prevent flutter echoes.

Structureborne Sound

Sound transmission through solid material by means of vibrations or waves in the material.

Subjective

Related to conditions of the brain and sense organs rather than direct physical actions.

Threshold of Audibility

The minimum sound pressure level capable of evoking an auditory sensation.

Threshold of Pain

The minimum sound pressure level of sound which stimulates the ear to the point at which discomfort gives way to definite pain.

Tone

The subjective response of the ear to the pitch of a sound.

Ultrasonic

Sound above the audible range with a frequency greater than $20,000\,Hz$.

Velocity of Sound in Air

The rate of travel of sound, considered a constant $330\,m/s$ or approximately $1130\,ft/s$ in architectural acoustics.

Waveform

The shape of the graphic representation of a sound wave.

Wavefront

The spherical surface of the wave as it travels out in all directions from the source.

Wavelength (\lambda)

The distance sound travels during one cycle of vibration, calculated as λ= v/f

Room Acoustics

The qualities or characteristics of a room, auditorium or concert hall that determine the audibility of speech or fidelity of musical sounds in it.

Architectural Acoustics

A branch of acoustics that deals with providing rooms and buildings with good conditions for listening to speech and music. It plays an important role in the

Engineering Acoustics

The technology of sound production and recording, sound motion pictures, and radio and television, as well as the study of vibrations of solids and their control and the use

Environmental Acoustics

involves the control of noise pollution, environmental noise includes automobile and other motor vehicles, aircraft, industrial plant and heavy construction equipment.

Underwater Acoustics

deals specifically with all aspects of sound in the sea and its use for detection of vessels and exploration of the seabed.

Bioacoustics and Medical Acoustics

use sound (particularly at high frequency) in medical diagnosis and therapy as well as its use in the study of overall behavior of animals in general.

Physiological and Psychological Acoustics

Acoustics deals with hearing in humans and animals.

Musical Acoustics

deals with the physics of musical instruments.

Speech or Communication Acoustics

considers the production and transmission of speech.

Basic elements in an acoustical situation

Source

human speech, mechanical equipment, etc.

Basic elements in an acoustical situation

Path

air, earth, building materials, water, etc.

Basic elements in an acoustical situation

Receiver

usually humans, although sometimes animals or sensitive medical equipment