A decibel is

A decibel (dB) is a logarithmic unit used to measure sound level, intensity, or sound pressure [t1][t2]. It is named in honor of Alexander Graham Bell and is used to quantify how loud a sound is perceived by the human ear [t2][t3]. Unlike linear scales, the decibel scale is logarithmic to better represent the human perception of sound intensity changes [t2]. While frequency is measured in Hertz and wavelength refers to the physical length of a sound wave cycle, the decibel specifically expresses the amplitude or power level of the sound [t3][t4][t5]. Standard measurements indicate that normal conversation occurs at approximately 60 dB, while noise levels above 90 dB can be harmful [t1][t2]. The World Health Organization and other health bodies use decibels to set safety standards for indoor and occupational noise exposure to prevent hearing loss [c1][c5][t6].

Sources

1. [1] https://www.nidcd.nih.gov/health/how-sound-measured
2. [2] https://www.nps.gov/teachers/classrooms/sound-intensity-and-loudness.htm
3. [3] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 5: Environmental Pollution > 5.7. NOISE POI,LUTION > p. 80
4. [4] INDIA PEOPLE AND ECONOMY, TEXTBOOK IN GEOGRAPHY FOR CLASS XII (NCERT 2025 ed.) > Chapter 9: Geographical Perspective on Selected Issues and Problems > Noise Pollution > p. 98
5. [5] http://www.osha.gov/otm/section-3-health-hazards/chapter-5