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Measurement
Published in Carl Hopkins, Sound Insulation, 2020
Measured levels in one-third-octave-bands are sometimes combined to give the octave-band level. Figure 3.6 shows the three one-third-octave-band filters that would be combined to form the 1000 Hz octave-band alongside the 1000 Hz octave-band filter itself. This shows a marked difference between the rolloff slopes for one-third-octave and octave-band filters. Hence there can be differences between levels measured with octave-band filters, and octave-band levels calculated from measurements with one-third-octave-band filters. The extent of these differences depends on the shape of the spectrum. To avoid dispute it is possible to require that measurements be taken in one-third-octave-bands, and that these measured values are used to calculate the octave-band values.
Instrumentation for Sound and Vibration Measurement
Published in Malcolm J. Crocker, A. John Price, Noise and Noise Control, 2018
Malcolm J. Crocker, A. John Price
Piezoelectric accelerometers and integrators have already been discussed in Sections 3.5.2 and 3.5.3. These items can satisfactorily be used to replace a microphone and transform a sound level meter into a portable vibration meter capable of measuring acceleration, velocity, and displacement. Figure 3.81 shows a precision sound level meter and an integrator and accelerometer connected. With this particular sound level meter, interchangeable scales are provided so that acceleration, velocity, and displacement can be read directly off the meter scale with the integrator switched to give a linear response, and one or two stages of integration, respectively. An octave or one-third octave filter set can be attached to the sound level meter in order to analyze the vibration signal into frequency bands.
Acoustic Signal Processing
Published in Richard C. Dorf, Circuits, Signals, and Speech and Image Processing, 2018
Juergen Schroeter, Gary W. Elko, M. Mohan Sondhi, Vyacheslav Tuzlukov, Won-Sik Yoon, Yong Deak Kim
The principal areas of interest to humans have been acoustic pressure threshold for hearing; acoustic threshold of damage to hearing; threshold for speech communication in the presence of noise; and community response to annoying sounds. The vast amount of data required to evaluate human responses, and then to communicate the recommendations to laymen, forced psychoacousticians and noise-control engineers to adopt simple instrumentation and a simple vocabulary that would provide simple numbers for complex problems. Originally this was appropriate to the analog instrumentation. But even now digital measurements are reported according to former constraints. For example, the octave band, which is named for the eight notes of musical notation that corresponds to the 2:1 ratio of the top of the frequency band to the bottom, remains common in noise-control work. For finer analysis, one-third octave band instruments are used; they have an upper-to-lower-band frequency ratio of 20.33, so that three bands span one octave.
Development of an intervention program to reduce whole-body vibration exposure based on occupational and individual determinants among dumper operators
Published in International Journal of Occupational Safety and Ergonomics, 2023
Rahul Upadhyay, Amrites Senapati, Kenora Chau, Ashis Bhattacherjee, Aditya Kumar Patra, Nearkasen Chau
The vibration evaluation procedure incorporates a method of averaging vibration level over time and frequency band using a one-third octave band. The human response to WBV is not uniform along all axes. Therefore, weighting filters are used to evaluate it. These weightings are based on potentially harmful effects connected to each frequency. For a seated person, two principal weightings are used for the measurement of WBV. These are Wd for the x and y axes, and Wk for the z axis [45,47,54]. For this study, root mean square acceleration (rmsa) along the dominant axis (z axis) was used as the WBV measurement. Daily exposure, A(8), was also calculated to quantify exposure during an 8-h shift [45,47]. In the present study, the daily exposure, A(8), is estimated from the rmsa in the dominant axis (awz).
An interval statistical energy method for high-frequency analysis of uncertain structural–acoustic coupling systems
Published in Engineering Optimization, 2020
J. H. Dong, F. W. Ma, Y. D. Hao, C. S. Gu
The engine compartment was the most significant source of noise in the vehicle, which propagated to the interior acoustic cavity through the firewall. Therefore, firewall insulation was one of the most important criteria for evaluating noise suppression performance. This assessment was conducted by measuring the sound pressure or vibrational energy of the interior vehicle cavity during transmission of a 1 W input signal across the full frequency band. A one-third octave method was adopted for calculation across a range of 400–8000 Hz.