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Personal sound amplification products are ear-level amplification devices intended for use by persons with normal hearing. The output levels of 27 PSAPs that were commercially available in Europe were analyzed in 2014. All of them had a maximum output level that exceeded 120 dB SPL; 23 (85%) exceeded 125 dB SPL, while 8 (30%) exceeded 130 dB SPL.
Music played at 85 decibels, or level of sounds, for prolonged periods of times can cause hearing damage, for instance, sound levels at some rock concerts can reach 110-120 A-weighted decibels, and at those levels, the maximum daily limit set by most standards and regulations can be reached in less than one minute of exposure. [8] [9]
1 LU corresponds to the relative measurement of 1 dB on a digital scale. LU can also express the difference in level from the target level. [5] In a loudness meter implementing EBU Mode: Reference level = −23 LUFS = 0 LU A programme with an integrated loudness of −26 LUFS measures −3 LU in EBU Mode (i.e. is 3 LU quieter than the target ...
The first research on the topic of how the ear hears different frequencies at different levels was conducted by Fletcher and Munson in 1933. Until recently, it was common to see the term Fletcher–Munson used to refer to equal-loudness contours generally, even though a re-determination was carried out by Robinson and Dadson in 1956, which became the basis for an ISO 226 standard.
Practical considerations of acceptable distortion levels in microphones combined with typical practices in a recording studio result in a useful dynamic range of 125 dB. [ 28 ] : 75 In 1981, researchers at Ampex determined that a dynamic range of 118 dB on a dithered digital audio stream was necessary for subjective noise-free playback of music ...
Signal-to-noise ratio (SNR), however, is the ratio between the noise floor and an arbitrary reference level or alignment level. In "professional" recording equipment, this reference level is usually +4 dBu (IEC 60268-17), though sometimes 0 dBu (UK and Europe – EBU standard Alignment level).
1 dB = 1 / 20 ln(10) is the decibel. The commonly used reference sound intensity in air is [ 5 ] I 0 = 1 p W / m 2 . {\displaystyle I_{0}=1~\mathrm {pW/m^{2}} .} being approximately the lowest sound intensity hearable by an undamaged human ear under room conditions.
LKFS and LUFS are identical in that they are both measured in absolute scale and both equal to one decibel (dB). [12] Loudness units (LU) is an additional unit used in EBU R128. It describes L k without direct absolute reference and therefore describes loudness level differences.