Building Utilities 3 - Architectural Acoustics Week 1

Building Utilities 3 - Architectural Acoustics and Lighting - Week 1

• This week's topic is architectural acoustics and lighting.
• Acoustics is the science of sound and vibration, encompassing stress fluctuations and waves in a material medium. It also includes the art and science of designing spaces and buildings for comfort and communication. In buildings, acoustics deals with generating, transmitting, and absorbing sound to create desired conditions.
• All acoustic situations share three common elements: a source (which can be altered in volume), a transmission path (that can be modified to transmit more or less sound), and a receiver (a listener with a typical auditory range of 20 to 20,000 Hz).
• Various types of acoustics exist, including psychoacoustics (human response to sound), environmental (impact of the environment on sound), architectural/room acoustics (space and structure design for hearing needs), electroacoustics (creation and detection of sound waves), and sonics (applying sound principles in science, industry, and medicine).
• Sound is a physical wave, a mechanical vibration, or pressure variations in an elastic medium. Airborne sound uses air as the medium, while structure-borne sound uses a combination of materials like concrete, steel, wood, etc. Sound is felt as a sensation via pressure change in the medium (particle displacement in velocity).
• Sound sources include speech, music, and noise (produced by impact or vibrating bodies.
• Sound wave characteristics include amplitude (pressure/loudness), wavelength, and speed (at 1130 ft/sec or 344 m/sec at normal room temperature). Sound speed increases in denser materials. The intensity rate represents sound energy transmission.
• Sound intensity diminishes with distance. Decibels measure sound intensity; a decibel-meter measures it.
• Sound properties include sound pressure (fluctuation in atmospheric pressure due to vibrations), wavelength (distance traveled during a cycle), and loudness (subjective sensation on a soft-to-loud scale).
• The threshold of audibility is the minimum sound intensity to evoke an auditory response, while the threshold of pain is the maximum.
• Frequency, measured in Hertz (cycles per second), describes the number of oscillations a particle undergoes. Pitch is the auditory system's ability to pinpoint sounds on a high-to-low frequency scale, and tone is a subjective sound sensation with pitch.
• Sound directionality changes based on reflective surfaces. High-frequency sounds are more noticeable along the source’s longitudinal axis.
• Natural elements affecting sound include temperature, clouds, wind, and bodies of water. The characteristics of surfaces influence sound. Flat surfaces reflect sound uniformly, convex surfaces disperse it, and concave surfaces concentrate it. Sound can be reflected, absorbed, diffused, diffracted, transmitted or dissipated.
• Sound refraction describes a change in sound direction as it moves between mediums of different densities. Sound transmission occurs when sound penetrates a surface.