• Abbreviation of decibel sound pressure level. A measurement of sound pressure, expressed in decibels, with respect to the threshold of hearing. The threshold of hearing is usually defined as 20 micropascals, which is assigned a value of 0 decibels. For example, leaves gently rustling produce a sound level of approximately 15 dB SPL, a whisper is about 30 dB SPL, the dial tone of a telephone is more or less 80 dB SPL, and an approaching subway train is somewhere around 110 dB SPL. Naturally, each of these approximations may vary quite a bit. For instance, the type of train, its approaching speed, and station acoustics are some of the factors which affect a dB SPL reading in the case of a subway. For a person with good hearing, pain begins somewhere around 120 dB SPL, and there is immediate damage to hearing above 150 dB SPL. Also called sound pressure level (1).
  • synonymdecibel sound pressure level