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Our Environment
Published in Karlheinz Spitz, John Trudinger, Mining and the Environment, 2019
Karlheinz Spitz, John Trudinger
The environmental effects of sound and human perceptions of sound can be described in terms of four characteristics, pressure, frequency, duration, and pure tone. Sound pressure level (SPL, also identified by the symbol Lp) or perceived loudness is expressed in decibels (dB) or a weighted decibel scale dB(A) which is weighted towards those portions of the frequency spectrum, between 20 and 20,000 Hertz, to which the human ear is most sensitive. Both measure sound pressure in the atmosphere. Frequency (perceived as pitch) represents the rate at which a sound source vibrates or makes the air vibrate. Duration represents recurring fluctuation in sound pressure or tone at an interval; sharp or startling noise at recurring interval; the temporal nature (continuous vs. intermittent) of sound. Pure tone is sound comprising a single frequency, relatively rare in nature but, if pure tone does occur, it can be extremely annoying.
An Introduction to Sound, Hearing and Perception
Published in Nick Zacharov, Sensory Evaluation of Sound, 2018
In most cases when a sound is amplified to have a higher sound pressure level (SPL), the perceived loudness will be higher. Loudness is a quantity that reflects the perception of the strength of sound by the listener in scale from silent to loud, which will be discussed more in Section 3.3. However, the SPL does not estimate generally the perceived loudness for many reasons, one being the fact that the subjective level perception is strongly frequency-dependent, as can be easily seen from the equal loudness contours of the hearing system (ISO 226, 2003) shown in Figure 3.1. This curve was measured using subjects who compared a 1 kHz reference tone at a given SPL and a test tone of another frequency by adjusting the latter to have the same perceived loudness. As can be seen in the figure, the contours show a prominent dependence on frequency.
Instrumentation for Noise Measurement and Analysis
Published in David A. Bies, Colin H. Hansen, Engineering Noise Control, 2017
David A. Bies, Colin H. Hansen
The A-weighting circuit was originally designed to approximate the response of the human ear at low sound levels. Similarly, B and C networks were intended to approximate the response of the ear at levels of 55-85 dB and above 85 dB, respectively. The characteristics of these networks are shown in Figure 3.5, with 1/3 octave band values tabulated in Table 3.1. A fourth network, the D-weighting, has been proposed specifically for aircraft noise measurements. However, it has not gained favour and instead, the C-weighting network is currently used for aircraft noise characterisation. For all other noise measurements, the trend appears to be toward exclusive use of the A-weighting network. This is because the A-weighting curve is a good approximation of the ear response to low level sound such as may be typical of environmental noise. Hearing loss as a result of exposure to high level industrial noise also seems to be a function of the A-weighted sound level, even though the apparent loudness of high level noise is closer to the C-weighting curve.
Degenerate brainstem circuitry after combined physiochemical exposure to jet fuel and noise
Published in Journal of Toxicology and Environmental Health, Part A, 2022
O’neil W. Guthrie, Brian A. Wong, Shawn M. McInturf, David R. Mattie
Auditory symptoms such as tinnitus, hyperacusis, poor speech discrimination (especially in noise) and loudness intolerance are associated with a degenerate auditory brainstem circuit (Auerbach, Rodrigues, and Salvi 2014; Schaette and McAlpine 2011; Valderrama et al. 2018). Patients who present with tinnitus exhibit different brainstem circuits compared to controls yet yield brainstem circuit performances that might approximate that of control. Several investigators reported that patients who suffer with tinnitus exhibit dysfunctional early waves of the ABR yet simultaneously exhibit late ABR waves that resemble those of controls (Bramhall, Konrad-Martin, and McMillan 2018; Gu et al. 2012; Schaette and McAlpine 2011). This pathologic condition is often referred to as central gain or central compensation (Sedley 2019). Similar observations may be seen for subjects who suffer with hyperacusis, poor speech discrimination in noise and loudness intolerance. Here, both humans and animals present with dysfunctional early waves of the ABR relative to controls (an indication that brainstem circuits are different relative to normal) yet they also exhibit late wave ABRs that approximate those of controls (an indication of similarity in brainstem circuit performance) (Refat et al. 2021; Valderrama et al. 2018; Zeng 2013).
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.