Simple Explanation

A measure of the volume or loudness of sound, expressed in decibels (dB).

Concise Technical Definition

Sound Pressure Level (SPL) is a unit used to quantify the intensity of sound in terms of air pressure variations. It is measured in decibels (dB), which is a logarithmic scale that compares the sound pressure with a reference level. SPL is often used to express the loudness of sound, with a 10 dB increase requiring 10 times the power but only making the sound seem twice as loud. A typical SPL for live orchestral music can reach around 105 dB, while rock concerts often exceed 120 dB. SPL can also be referenced relative to the sensitivity of human hearing or an absolute value in Pascals.

Layman-Friendly Analogy

SPL is like the "volume" of sound—just as you can adjust the volume on a speaker to make music louder or quieter, SPL is a way to measure how loud a sound is. A higher SPL means the sound is louder. It's measured in decibels, so when the SPL goes up by 10 dB, the sound becomes about twice as loud to our ears, but it actually takes 10 times more power to produce that extra loudness.

Industry Usage Summary

SPL is widely used in audio engineering and acoustics to measure the intensity of sound in different environments. It is crucial for determining safe listening levels, optimizing sound reinforcement systems, and designing spaces with appropriate acoustics. In live sound, SPL is used to assess and control the loudness of performances, ensuring that audio levels are appropriate for the space and audience. SPL is also an important factor in evaluating speaker performance, noise pollution, and hearing safety. Audio professionals and engineers regularly measure SPL to maintain clear, intelligible sound without exceeding recommended volume levels.

Engineering Shortcut

A measure of the loudness of sound, expressed in decibels (dB).

Full Technical Explanation

SPL (Sound Pressure Level) is a logarithmic measurement of sound intensity, used to quantify the pressure variations in the air caused by sound waves. It is measured in decibels (dB), a unit that expresses the ratio of sound pressure relative to a reference level, often defined as 20 µPa, the threshold of hearing. A 10 dB increase in SPL means the sound intensity has increased tenfold, but to the human ear, it only appears about twice as loud. SPL is used to characterize sound across a wide range of applications, from live music and sound reinforcement to noise control and hearing protection. In typical conditions, live orchestral music peaks around 105 dB SPL, while rock concerts can exceed 120 dB SPL. SPL is also sometimes given in Pascals (Pa) for an absolute sound pressure measurement, with 1 Pascal corresponding to 94 dB SPL.