Category: (((—Acoustics Engineering—))))
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Dynamic Range
It is seen for the microphone (or accelerometer) shown in Figure 7.3 that the dynamic range is about 100 dB. Most good‐quality microphones have a dynamic range of about 100–120 dB (interestingly enough about the same as the human ear) [2]. As the microphone diaphragm diameter (or accelerometer mass) is increased, the transducer sensitivity is normally increased as well…
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Sensitivity
An ideal microphone (or accelerometer) together with its measurement system should have an output voltage amplitude E that is proportional to the exciting pressure amplitude p (or acceleration amplitude a) (see Figure 7.2). The ratio of open‐circuit output voltage to input pressure (or acceleration) is normally called the sensitivity Mp: (7.1) The transducer sensitivity [V/(N/m2) or V/(m/s2)] depends on the microphone (or…
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Transducer Characteristics
An ideal sound or vibration transducer should have the following characteristics [1]: No transducer can meet all of the above criteria, and thus different types of transducers and vibration sensors are preferred for different measurements. The microphone is by far the most common form of acoustical transducer, and the piezoelectric accelerometer is the most widely…
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Transducers
The basis of all noise and vibration measurement systems is the transducer. The microphone is the main transducer used to measure sound, while the accelerometer is the main transducer used to measure vibration. Specialized transducer systems have been developed to measure sound intensity in air and vibration intensity of structural systems. In addition, measurement procedures…
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Typical Measurement Systems
It may be necessary to measure noise and/or vibration for various reasons. Before beginning any measurement program, the objectives should be defined. For instance, it may be desired to measure noise to determine if a noise problem exists, whether the noise output of a machine is within its specifications, to determine the main sources of…
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Introduction
In the measurement of noise and vibration fields, it is necessary to sense the sound or vibration disturbance with a transducer. The transducer converts some physical property of the sound and vibration field into an electrical signal. This signal is then amplified, attenuated, or transformed in some way so that it can be analyzed and/or…
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Human Vibration Criteria
The effects of vibration on people’s health and criteria for protection are discussed in Chapter 5. Criteria for human comfort and annoyance, in particular for vibration in buildings, are discussed in this section. 6.17.1 Human Comfort in Buildings Vibration discomfort depends on many factors including the characteristics of the vibration. Most standards are designed to assess…
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Noise Criteria and Noise Regulations
Using some of the noise measures and descriptors discussed and surveys and human response studies, various criteria have been proposed so that noise environments can be determined that are acceptable for people, for speech communication, for different uses of buildings, for sleep, and for different land uses. In some countries such criteria are used to write…
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Human Response
6.15.1 Sleep Interference Various investigations have shown that noise disturbs sleep [56–62]. It is well known that there are several stages of sleep and that people progress through these stages as they sleep [56]. Noise can change the progression through the stages and if sufficiently intense can awaken the sleeper. Most studies have been conducted…
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Evaluation of Community Noise
In some community noise measures, corrections are applied to community noise levels to account for pure‐tone components or impulsive character, seasonal corrections (summer or winter when windows are always closed), type of district (rural, normal suburban, urban residential, noisy urban, very noisy urban), and for previous exposure (such corrections are similar to those for NR).…