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Sound field, spatial hearing, and sound reproduction
Published in Bosun Xie, Spatial Sound, 2023
Auditory distance perception, which was thoroughly reviewed by Zahorik et al. (2005), is a complex and comprehensive process based on multiple cues. Subjective loudness has been considered an effective cue to distance perception. Generally, loudness is closely related to sound pressure or intensity at a listener’s position; usually, strong sound pressure results in high loudness. In a free field, the sound pressure generated by a point sound source with constant power is inversely proportional to the distance between the sound source and the receiver (the 1/r law); that is, the SPL decreases by 6 dB for each doubling of the source distance. As a result, a close distance corresponds to a high sound pressure and subsequent high loudness. As such, loudness becomes a cue for distance estimation. However, the 1/r law only applies to the free field and deviates in reflective environments. Moreover, the sound pressure and loudness at a listener’s position depends on source properties, such as radiated power. Previous knowledge on sound sources or stimuli also influences the performance of distance estimation when loudness-based cues are used. In general, loudness is regarded as a relative distance cue unless the listener is highly familiar with the pressure level of the sound source.
Human factors in maintainability
Published in B.S. Dhillon, Reliability, Maintainability, and Safety for Engineers, 2020
where SPL is the sound-pressure level expressed in decibels.SP2 is the sound pressure, squared, of the sound to be measured.Pf2 is the standard reference sound pressure squared, representing zero decibels. Under normal circumstances, Pf is the faintest 1000 Hz tone that an average young person can hear.
Hearing, Sound, Noise, and Vibration
Published in R. S. Bridger, Introduction to Human Factors and Ergonomics, 2017
The amplitude of sound is evaluated by measuring the sound pressure level (SPL). The range of SPLs to which the human ear is sensitive is so wide (0.00002–20 N/m2) that linear scaling would present a problem. For this reason, a logarithmic scale—the decibel scale—is used. The decibel is a dimensionless unit related to the logarithm of the ratio of the measured SPL to a reference level (usually taken to be the threshold of hearing). The smallest noticeable difference in intensity between two sounds is about 1 dB. Commercial sound level (SL) meters measure and display an root-mean-square (rms) SPL, Lp, where Lp=20log10(p/pr)dB where Lp is the SPL in decibelsp is the sound pressure in Newtons per square meterpr is the reference SPL (0.00002 N/m2)
Low-Noise pavement technologies and evaluation techniques: a literature review
Published in International Journal of Pavement Engineering, 2022
Peter Mikhailenko, Zhengyin Piao, Muhammad Rafiq Kakar, Moises Bueno, Sahand Athari, Reto Pieren, Kurt Heutschi, Lily Poulikakos
Field tests are vital for noise assessment of low-noise pavements, but are also subject to the variability of the in-situ environment. Pavement noise levels can either be measured by moving on-board microphones or with non-moving microphones capturing vehicle pass-bys. These express the noise in terms of the A-weighted sound pressure level (SPL), which is weighted to account for the frequency-dependent sensitivity of human hearing and is expressed as dB(A) (Nilsson 2007). Highest weights are applied in the 1–5 kHz range as shown in Figure 2. Additionally, the sound absorption of the asphalt can also be measured in the field.
Effect of tip rake angle on the hydrodynamic characteristics and sound pressure level around the marine propeller
Published in Ships and Offshore Structures, 2018
Hassan Ghassemi, Mohsen Gorji, Jalal Mohammadi
In addition, the overall SPL decreases as the distance from the sound source increases. In the far field where sound propagates as spherical waves and kr >> 1 (k is the wave number and r is the distance to sound source) sound pressure follows the inverse square law with respect to the distance. This means that, in the far-field, the overall SPL is identified with the reverse square of the distance. For instance, if the distance doubles, the overall SPL reduces around 6–7 dB (Tian et al. 2014), so SPL for y/D = 1 and y/D = 2 is varied about 7 dB.
Aerodynamic noise prediction and reduction of H-Darrieus vertical axis wind turbine
Published in Australian Journal of Mechanical Engineering, 2023
Figure 7 shows the distance effect between the source and receivers; the SPL is computed in five different distance from the rotor for rotational speed 100, 200, 300 and 500 rpm. The results indicate that the SPL depends on the distance between the noise receivers and source. The SPL spectrums have significant tonal peaks at each distance. However, for the same rotational speed, the characteristics of the SPL and the position of these peaks is consistent. Therefore, we can infer that the aerodynamic noise is decreased with the addition of the receivers distance from the Figure 7.