1. ARCHITECTURAL ACOUSTICS
ACOUSTICS: branch of physics concerned with sound deals with the production, control, transmission, reception, and effects of sound 3 parts (elements): 1. Sound Source ( e.g. human speech, HVAC equipment) 2. Transmission Path (e.g. air, earth, building materials) 3. Receiver (e.g. humans, animals, sensitive medical equipment)

2. Definitions of SOUND physical wave in an elastic medium, usually air
the sensation stimulated in the organs of hearing by mechanical radiant energy transmitted as longitudinal pressure waves through the air or other medium
a vibration in an elastic medium such as air, water, most building materials, and the earth
physically, sound is a rapid fluctuation of air pressure

3. ARCHITECTURAL ACOUSTICS
technology of designing spaces, structures and mechanical systems to meet hearing needs
effect of building design on the control of sound in buildings
3 Aspects of Acoustical Design in Buildings
1. Planning to keep noise sources as far as possible from quiet area
2. Internal acoustics of rooms
3. Structural precautions to reduce noise penetrations

4. Types of Sound
Wanted Sound (speech, music) – heard properly; considered desirable
Unwanted Sound (noise) – annoyance; not desired or objectionable
Characteristics of Sound
Audible
Inaudible

5. TERMINOLOGIES
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
Wave – a disturbance or oscillation that transfers energy progressively from point to point in a medium or space without advance by the points themselves, as in the transmission of sound or light
Sound Wave – a longitudinal pressure wave in air or an elastic medium esp. one producing an audible sensation

6. the no. of cycles per unit time of a wave or oscillation
TERMINOLOGIES
Frequency
the no. of times the cycle of compression and rarefaction of air occurs in a given unit of time (e.g cycles in the period of 1 second = 1000 cps = 1000 Hertz)
the no. of cycles per unit time of a wave or oscillation
the no. of complete cycles per second (frequency of vibration)
the rate of oscillation of molecules by sound (frequency of vibration) measured in cycles per second (Hertz)
Pitch – frequency of sound vibration; the predominant frequency of a sound as perceived by the human ear
Vibration – the back and forth motion of a complete cycle
Cycle – full circuit by a displaced particle
Period – the time required for one complete cycle

7. 20 – 20,000 Hz – approx. audio frequency range of human hearing;
TERMINOLOGIES
Frequency
20 – 20,000 Hz – approx. audio frequency range of human hearing;
600 – 40,000 Hz – critical frequency for speech communication
Tone – composed of a fundamental frequency with multiples of the fundamental, called Harmonics
Pure Tone – sound composed only of 1 frequency
Musical sounds are combination of many pure tones
Frequency bands – used to express division of sounds into sections (Octave bands are the most common)
9 Octave Bands – 31.5, 63, 125, 250, 500, 1000, 2000, 4000, 8000 Hz

8. TERMINOLOGIES
Velocity
varies according to the medium of transmission; approx fps in air at normal temperature and pressure
Wavelength
Distance between similar points on successive waves; the distance the sound travels in one cycle
Relationship between wavelength, frequency, and velocity:
Λ = c/f
Λ = wavelength, ft.2
c = velocity of sound, fps
f = frequency of sound, Hz (cps)
Low frequency sounds: characterized by long wavelengths
High frequency sounds: characterized by short wavelengths
Sounds with wavelengths ranging from ½” – 50’ can be heard by humans, 1000, 2000, 4000, 8000 Hz

9. Sound power (watts) – amount of energy produced by a source
TERMINOLOGIES
Magnitude
Sound power (watts) – amount of energy produced by a source
Intensity – describes the energy level; unit is watts/cm2
Loudness (what is perceived) – related to the Intensity Level (IL) or Sound Pressure Level (SPL)
The Sound Pressure Level (SPL) is equivalent to the Sound Intensity Level (IL)
Intensity Level is expressed in decibels
Decibel – dimensionless unit used to express the ratio of two numerical values of a logarithmic scale

10. ROOM ACOUSTICS Sound Indoors – Acoustics of Room
Sound Absorption - some absorb low frequency energy; some absorb high frequency energy
Noise Reduction by Absorption
Noise levels in a room are highest for a given source if the room’s surfaces are primarily sound reflecting; lowest if there are large areas of sound absorbing materials (e.g. sound absorbing ceilings
Reflections – sound foci/diffused
Reverberation – prolongation of sound; persistence