BOOK_CONTENT
From HVAC Systems Design Handbook, Fourth Edition

20.1 Introduction

The HVAC designer cannot neglect consideration of the sound and vibration generated by HVAC equipment. This chapter briefly discusses the fundamentals of sound and vibration control. References for further study are cited at the end of the chapter.

20.2 Definitions

Sound is a form of energy, detected as a variation in pressure and stress in an elastic or viscous medium. The traditional concept is that sound is generated by a source and is transmitted through a path to a receiver (Fig. 20.1). Diminishment of the sound during transmission is called attenuation. The receiver is usually a human ear or a microphone. The audible range of hearing for humans is roughly between 20 Hertz (Hz) and 20,000 Hz. Many animals have a wider range. Lower frequencies can sometimes be felt.


Figure 20.1: Sound transmission.

Vibration is a form of energy, detected as cyclic movement in a machine or structure. Sound and vibration are mutually convertible, and many transmission problems and solutions depend on this fact.

Noise is unwanted sound. One person s sound may be another person s noise, e.g., heavy-metal rock music. In general, however, noise is random sound. White noise, used for masking unwanted sound, is random sound in the speech interference range.

20.3 Methods of Specifying and Measuring Sound

There are several ways of describing the characteristics of sound: sound power, sound pressure, intensity, loudness, frequency, speed, and directivity.

Sound power

An acoustical source radiates energy in the form of sound. This acoustical power is expressed...

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Products & Services
Active Noise Control Products
Active noise and vibration control systems are products such as controllers, sensors and actuators that monitor and cancel noise and/or vibration.
Sound Level Meters and Noise Dosimeters
Sound level meters and noise dosimeters are used in sound and noise analysis. Applications include industrial safety, traffic noise studies, and scientific noise measurement.
Noise, Vibration, and Harshness (NVH) Test Equipment
Noise, vibration, and harshness test equipment are equipment used to test and monitor noise, vibration, and harshness in mechanical and electrical systems.
Acoustical Design Services
Acoustical design services design rooms, buildings, theaters, churches, courthouses and schools, paying special attention to the reflection of sound waves.
Soundproofing and Acoustic Materials
Sound proofing and acoustic materials are used to attenuate, deaden, or control sound and noise levels from machinery and other sources for environmental amelioration and regulatory compliance. 

Topics of Interest

21.1 Background The concept of indoor air quality (IAQ) is not new. Publications as far back as the early 1800s discuss the subject and suggest ventilation as the solution. These early writers mostly...

Acoustics is the science of sound and vibration. The control of sound and vibration transmission within a structure involves architectural design and structural, mechanical, and electrical engineering...

Acoustics is the science of sound and vibration. The control of sound and vibration transmission within a structure involves architectural design and structural, mechanical, and electrical engineering...

Vibration is a mechanical phenomenon whereby oscillations occur about an equilibrium point. The oscillations may be periodic such as the motion of a pendulum or random such as the movement of a tire...

2.1 Introduction When airborne sound from the human voice is transmitted from one room to another, the resulting vibration on the walls and floors in the receiving room is at a sufficiently low level...