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Airborne Sound
Published in Dhanesh N. Manik, Vibro-Acoustics, 2017
The sound pressure at various octave bands can be measured using a microphone and associated frequency filters. This cannot give an objective assessment of sound as perceived by the listener, since our ears have a nonlinearly varying sensitivity to sound at different frequencies. One of the first attempts to account for this was to define loudness in the form of phons. A phon was defined as the sound pressure level of a sound at 1000 Hz. Corresponding to each phon, a phon contour was drawn at various frequencies. This was done by subjective assessment of the sound pressure level corresponding the phon at 1000 Hz, to the sound pressure level at other frequencies, which have the same loudness as that of a sound at 1000 Hz.
Machine Learning in Acoustic DSP
Published in Francis F. Li, Trevor J. Cox, Digital Signal Processing in Audio and Acoustical Engineering, 2019
RMS levels (when RMS values are expressed in decibels) of a signal are directly related to the sound pressure levels. In the literature, some authors refer to the RMS level as “loudness.” However, in a strict sense, loudness is a measure of sound perception, not a physical measure of signals themselves. The relationships between sound pressure level and perceived loudness have been established; for example, the equal loudness contours give the relationships between the SPL (dB) and loudness (phon) for pure tones. The “loudness” used by some authors to mean RMS should not be confused with psychoacoustically defined loudness.
Noise and Vibration in Switched Reluctance Machines
Published in Berker Bilgin, James Weisheng Jiang, Ali Emadi, Switched Reluctance Motor Drives, 2019
James Weisheng Jiang, Jianbin Liang, Jianning Dong, Brock Howey, Alan Dorneles Callegaro
Up to now we have discussed how to calculate the physical noise caused by the magnetic forces. However, human ears have different levels of sensitivity depending on the frequency. To match our physiological perception of sound, weighting curves are commonly applied to the sound levels. In Figure 13.62, the A-weighting curve is approximately inverted from the 40 phon loudness contour. Phon is a unit of loudness level and it represents the SPL at a certain frequency that has an equal perceived loudness. The shape of the A-weighting curve is similar to the response of human ear at the lower noise levels. A-weighting curve is the predominant one in the electric machine industry out of the 4 weighting curves shown in Figure 13.62 [2]. The B-weighting curve was initially developed to cover the area between A and C curves. It was used heavily by the motor industry, but it is rarely used nowadays. The C-weighting curve is better at representing the human response to high noise levels. The D-weighting curve was developed to measure high level noise for aircraft. If the A-weighting curve is used to modify the SPL, the following equation can be used. () SPLA(f(q))=SPLA(f(q))+LA(f)
On the selection of stimulus for the auditory variant of the detection response task method for driving experiments
Published in Traffic Injury Prevention, 2018
Kristina Stojmenova, Franco Policardi, Jaka Sodnik
Loudness is a subjective measure (phon), and frequencies in the area between 2 and 5 kHz can be perceived as louder than other frequencies even when played with the same intensity (dB). Because Chocholle (1940) concluded that equal loudness signals, regardless of the frequency, resulted in the same response times, we played each signal at the same intensity but not at the same loudness.