Convert Bels to Decibels

Convert Bels (B) to Decibels (dB) instantly and accurately.

Conversion Formula

dB = B × 10

About Bels

The bel (B) is the original logarithmic unit of sound and signal level, defined as a tenfold power ratio: L = log₁₀(P₁/P₂) bels, or for field quantities L = 2 × log₁₀(A₁/A₂) bels. Introduced at Bell Telephone Laboratories in the 1920s and named in honour of Alexander Graham Bell (1847–1922), the bel was used to quantify telephone transmission line attenuation: 1 bel of loss meant output power was 1/10 of input. Because 1 bel represents a tenfold change - far too coarse for grading (even untrained listeners can detect a 1 dB = 0.1 B change) - the decibel replaced it in virtually all practical use. Key reference points: 0 B = equal-level reference; 3 B = 30 dB (1000:1 power ratio); 6 B = 60 dB (normal speech at 1 m); 12 B = 120 dB (pain threshold). A 1 B (10 dB) increase in SPL roughly doubles perceived loudness (Stevens’s power law at moderate intensities). 1 B = 10 dB = ln(10)/2 Np ≈ 1.151293 Np.

About Decibels

The decibel (dB) is the universal unit of sound level and signal level in acoustics, audio engineering, and telecommunications. Named in honour of Alexander Graham Bell (1847–1922), it was adopted by Bell Telephone Laboratories and CCITT in the 1920s–1930s. Sound pressure level: L_p = 20 × log₁₀(p/p₀), where p₀ = 20 µPa in air (ISO 1683). Key SPL reference points: 0 dB SPL = threshold of human hearing; 60 dB SPL = normal conversation at 1 m; 85 dB SPL = NIOSH 8-hour occupational limit; 120 dB SPL = pain threshold; 194 dB SPL = theoretical maximum undistorted plane wave in air at 1 atm. In digital audio (AES17, IEC 61606), 0 dBFS = maximum digital full-scale level. In RF engineering, 0 dBm = 1 mW; Wi-Fi signal strength ranges from −30 dBm (excellent) to −90 dBm (unusable). 1 dB = 0.1 B = ln(10)/20 Np ≈ 0.11513 Np.

Quick Reference Table

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