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Make Listening Safe is promoting the development of features in PLS to raise the users' awareness of risky listening practices. In this context, the WHO partnered with the International Telecommunication Union to develop suitable exposure limits for inclusion in the voluntary H.870 safety standards on "Guidelines for safe listening devices/systems."
[2] [14] The sound level is then measured at the position of the subject's head with the subject not in the sound field. [2] Minimal audible pressure involves presenting stimuli via headphones [2] or earphones [1] [14] and measuring sound pressure in the subject's ear canal using a very small probe microphone. [2]
Sound pressure or acoustic pressure is the local pressure deviation from the ambient (average or equilibrium) atmospheric pressure, caused by a sound wave. In air, sound pressure can be measured using a microphone, and in water with a hydrophone. The SI unit of sound pressure is the pascal (Pa). [1]
Sensitivity is a measure of how effectively an earpiece converts an incoming electrical signal into an audible sound. It thus indicates how loud the headphones are for a given electrical drive level. It can be measured in decibels of sound pressure level per milliwatt (dB (SPL)/mW) or decibels of sound pressure level per volt (dB (SPL) / V). [36]
An equal-loudness contour is a measure of sound pressure level, over the frequency spectrum, for which a listener perceives a constant loudness when presented with pure steady tones. [1] The unit of measurement for loudness levels is the phon and is arrived at by reference to equal-loudness contours.
A sound level meter (also called sound pressure level meter (SPL)) is used for acoustic measurements. It is commonly a hand-held instrument with a microphone . The best type of microphone for sound level meters is the condenser microphone, which combines precision with stability and reliability. [ 1 ]
For example, if a person’s actual blood pressure is 134, and blood pressure is measured on a dangling arm, the reading could end up over 140, which is considered to be stage 2 hypertension.
Choosing the most appropriate hearing protection device, both with appropriate level of attenuation and appropriate fit for the individual. [5] Ideally, the device should limit the sound intensity that reaches the ear to levels below 85 dBA. If the attenuation does not limit the noise levels to that level, other alternatives should be sought.