UTY ACOUSTICS QUIZ

Electro Acoustics

Deals with the generation and detection of audible sound waves.

Psycho Acoustics

Deals with the reaction of human beings to audible sound.

Environmental Acoustics

Deals with the effects of the environment upon audible sound waves. This may be broken down to Architectural Acoustics and Landscape Acoustics.

Sonics

Deals with the technical application of mechanical waves in basic scientific research, industry, and medicine.

Key Framework Elements

Sources Of Sound, Sound We Cannot Hear, Natural Elements That Affect Sound

Sound

Form of energy that continues to subsist until filtered through a material forming into heat by friction.

Source, Path, and Receiver

Basic Elements in an Acoustic Situation

Reflection

When sound bounces after hitting a surface

Absorption

When sound is absorbed after hitting a surface

Transmission

Sound that isn’t absorbed nor reflected, but passes through matter.

70 dB

Lawn mower, City Traffic — Damage in 4 hours (Beginning of damage after hours of exposure)

80-90 dB

Hairdryer, Garbage disposal — Damage in 2 hours

90-95 dB

Electric drill — Damage in 1 hour

97 dB

Motorcycle — Damage in 30 minutes

100 dB

MP3 player, Snowmobile — Damage in 15 minutes

110 dB

Jet engine at take-off, Gunshot — Immediate hearing damage

118 dB

Leaf blower, Stadium football game — Damage in 30 seconds

120 dB

Rock concert, Ambulance siren — Damage in 8 seconds

120x10+dB

Fire alarm, Firecracker — Immediate safety hazard / Instantaneous damage

Echoes

When reflected sound arrives at approximately 70 msec or more after hearing the direct sound. Echoes, even if not distinctly discernable, are undesirable in rooms; they are annoying and make speech less intelligible. The relative annoyance is dependent on the time delay, and loudness relative to the direct sound which, in turn, are dependent on the size, position, shape, and absorption of the reflecting surface.

Late-Delayed Reflections

Similar to echo except that the time delay between the perception of direct and reflected sounds is somewhat less.

Sound Shadow

Occurs when an area does not receive an adequate amount of direct and reflected sound.

Sound Concentration

Sound reflections from concave surfaces concentrating in an area sometimes referred to as "hot spots". The intensity of sound at hot spots are always at the expense of dead spots.

Focusing

Concave domes, vaults, or walls will focus reflected sound into certain areas of rooms. This has several disadvantages. For example, it will deprive some listeners of useful sound reflection and cause hot spots at other audience positions.

Flutter Echo

A rapid succession of noticeable small echoes observed when a short burst of sound is produced between parallel sound reflective surfaces.

Coupled Spaces

Two rooms adjacent to each other by means of open doorways, with at least one space being highly reverberant.

Distortion

An undesirable change in the quality of musical sound due to the uneven and excessive sound absorption of the boundary surfaces at different frequencies.

Room Resonance (Coloration)

Occurs when certain sounds within a narrow band of frequencies tend to sound louder than other frequencies.

Whispering Gallery

High frequency sounds creeping along large concave surfaces such as a hemispherical dome. This describes the reflection of sound along a curved surface from a source near the surface. Although the sound can be heard at points along the surface, it is inaudible away from the surface.

Pre-Fabricated Units

Category 1: These include acoustical tile, which is the principal type of material available for acoustical treatments; mechanically perforated units backed with absorbent material; and certain wallboards, sheets, and batten structures.

Type 1

Cast Units Having a Pined or Granular Appearing Surface

Class A

Mineral units composed of small granular or finely divided particles with a portland cement binder.

Class B

Mineral units composed of small granules or finely divided particles with a lime or gypsum binder.

Class C

Unit composed of small granules or finely divided particles of mineral or vegetable origin with an incombustible mineral binder.

Category 2

Special Acoustical Products

Porous Absorbing Materials

Derived from animal sources (hair, wool, silk) and vegetable sources (cotton, flax, hemp).

Panel Resonators

An enclosed system of air inside a panel that communicates with the outside through small openings.

Volume Resonators

Designed to function primarily as specific narrow-band sound absorbers.

Porous Expanded Polypropylene Wall Panel (PEPP)

Typically made from porous materials that are designed to absorb sound waves rather than reflect them.

Melamine Foam (Wedge/Pyramid)

A nitrogen-rich compound. The melamine derivatives possess flame retardant properties due to the release of nitrogen when burned. Melamine reacts with formaldehyde and produces thermosetting plastic as a product. It extends good sound absorption since sound waves are absorbed over a broadband frequency range starting from 1,000 to 5,000 Hz where the sound absorption coefficient is higher than 0.6.

Acoustic Baffles (Sailcloth and Vinyl Encapsulated Baffle)

Cost-effective, lightweight, high acoustical performance, moisture and chemical resistant. Useful for any large area where noise and reverberation needs to be reduced. Sound waves are instead absorbed by the paneling; the baffle core is vibrated by sound waves on impact, converting the energy into heat before it is given a chance to return.

Acoustical Blankets

Category 3: made up chiefly of porous materials where the physical characteristics of the materials in each category are carefully considered.

Mineral wool, hair felt, wood fiber, and glass fiber

The materials used most commonly in the fabrication of acoustical blankets.

1-1/2 and 4 inches

The thickness of these blankets is generally between _____________. Blankets of greater thickness are sometimes used in special applications.

Noise

All sounds that are distracting, annoying, or harmful to everyday activities.

Airborne Noise

Sound transmitted through the air only, usually through continuous air paths (doors, windows, vents, air shafts, etc.). These pathways are called Acoustical Short Circuits.

Structure-borne Noise

Radiated sound resulting from the vibration of solid parts of the building structure.

Fundamental Objective

The fundamental objective of noise control is to provide an acceptable acoustical environment.

Land Use Planning & Urban Shielding

Utilizing commercial and open spaces as a buffer zone against heavy vehicular traffic noise.

Roadbeds Below Grade

Planning depressions and below-grade cuts (12 feet deep or more) intercepts direct line-of-sight sound propagation, achieving exceptional diffraction mitigation from highway systems.

Sound Path Principle

Every listener in a lecture hall, theater, or concert hall should hear the speaker or performer with the same degree of loudness and clarity.

Reflections

These occur when sound hits a surface that is neither predominantly absorptive nor sound transparent at the specific frequency. Non-absorptive surfaces that are large, as compared to the wavelength at a given frequency, reflect sounds.

Ray Diagram

a design procedure for analyzing reflected sound distribution throughout a hall, using the first reflection only.