These metrics can also be calculated in a number of different ways. Specific loudness is a compressive nonlinearity and varies at certain levels and at certain frequencies.
However, the reading from a sound level meter does not correlate well to human-perceived loudness, which is better measured by a loudness meter. The current international standard that specifies sound level meter functionality and performances is the IEC 61672-1:2013. Sound level meters are commonly used in noise pollution studies for the quantification of different kinds of noise, especially for industrial, environmental, mining and aircraft noise. Using this information, the instrument is able to accurately convert the electrical signal back to sound pressure, and display the resulting sound pressure level (unit decibel, dB). The instrument needs to know the sensitivity of the particular microphone being used. While describing sound in terms of sound pressure, a logarithmic conversion is usually applied and the sound pressure level is stated instead, in decibels (dB), with 0 dB SPL equal to 20 micropascals.Ī microphone is distinguishable by the voltage value produced when a known, constant root mean square sound pressure is applied. the sound pressure (unit pascal, Pa), is converted into an electrical signal (unit volt, V). That is why the instrument is sometimes referred to as a sound pressure level meter (SPL). The diaphragm of the microphone responds to changes in air pressure caused by sound waves. The best type of microphone for sound level meters is the condenser microphone, which combines precision with stability and reliability. It is commonly a hand-held instrument with a microphone. Logarithms (or logs for short) are simply a way of describing numbers which vary by very large amounts in a much smaller range.An integrating-averaging Cirrus Research's Optimus sound level meter which complies with IEC 61672-1:2002Ī sound level meter (also called sound pressure level meter ( SPL)) is used for acoustic measurements. Just about every piece of audio equipment (microphones, loudspeakers, sound cards, amplifiers, mixers, etc) will have specifications expressed as logarithms (i.e. We need to get familiar with the idea of a logarithm. The decibel is a better fit to how our brains perceive sound. The relationship between perceived loudness and the decibel is a straight line. On the next graph below, a logarithmic decibel scale is used and now the curve becomes a straight line. Our ’10x’ rule means that as the overall level increases, we need increasingly large changes in intensity to get a similar change in loudness. An intensity of 1,000 is also half as loud as an intensity of 10,000. So an intensity of 1,000 is twice as loud as an intensity of 100. To make a sound twice as loud, you need to multiply its intensity by about 10. In the graphs below, the x-axis represents the perceived loudness of a sound, and the y-axis represents the acoustic intensity needed to create that loudness. After analysis, I could offer various recommendations to rectify the issue − all distinctly individual from each other, as acoustics can be affected by nearly everything!” Rob Bungay, Acoustic Consultant, WSP What are decibels? To understand and try to reduce these causes of complaints, among other things I installed sound level meters throughout the room to record noise levels during the day and night, and used acoustic models of the space to assess changes within the room. “I recently worked on a multi-bed intensive care ward where patients and visitors were complaining about the intrusive noise made by the alarms from bedside monitors. In acoustical and audio engineering, decibels are used everywhere because knowing how loud a sound is important whether you’re assessing whether the noise from a new road is going to be a problem or setting the loudness of music in an arena. Graphic: Nick Maroulis Where are decibels used? When a sound is perceived to double in loudness, this corresponds to roughly an increase in 10 dB. It makes things easier if a logarithmic scale is used this is what the decibel scale is. The ratio of intensities between silence and ‘ow that hurts my ears’ is about 1:100 million million. The human ear is capable of hearing very quiet (low intensity) sounds and extremely loud (high intensity) sounds.