Background Noise

Background noise and sound insulation measurement for test rooms, meeting rooms, offices and production areas, with 1/1 or 1/3-octave analysis and comparison against the required criteria.

Background noise is the sound level in a room when the activity being tested is not running: air conditioning, machines, traffic and neighbouring areas. It decides whether a test room can be used for accurate measurement, and whether a meeting room or office is quiet enough for its purpose. How we measure: the sound level is recorded at several positions inside the room, and outside when the sound insulation of the room must be checked. Results include Leq, Lmax and Lmin in dB(A), and the spectrum in 1/1 or 1/3-octave bands. Where needed we use a test signal such as pink noise to check how evenly sound is distributed in the room and how much is blocked by its walls and doors. Measurements follow the agreed criteria, for example ASTM E1686. What you receive: a report with results at every position, spectrum charts, the difference between inside and outside, and a clear statement of whether the room meets the required criteria.

Key features

Measurement at multiple positions inside and outside the room
Leq, Lmax and Lmin in dB(A)
1/1 and 1/3-octave spectrum analysis
Sound insulation (inside / outside level difference)
Pink noise sound distribution tests
Report against the agreed criteria

Specifications

Measured values	Leq, Lmax, Lmin (dB(A))
Spectrum	1/1 octave or 1/3 octave, 12.5 Hz to 20 kHz
Guide	ASTM E1686
Sound level meters	Class 1 and Class 2 (IEC 61672-1)
Calibrator	Norsonic 1251 (IEC 60942 Class 1)

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Example projects

Bitwise: sound test room

Background noise measured at 5 positions inside and 4 positions outside a product sound test room, in 1/3-octave bands from 12.5 Hz to 20 kHz (ASTM E1686-03, September 2026).

Inside: 23.7 dB(A) average (Lmax 27.5, Lmin 22.1)
Outside: 66.6 dB(A) average
Noise reduction of the room: about 42.9 dB(A)
Very low background level for product testing

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Metropolitan Electricity Authority: meeting room

Pink noise test of the sound system and room insulation in a 5th-floor meeting room at the Khlong Toei head office: 9 positions inside and 3 outside (June 2026).

Target 80 dB(A) ±3 dB: measured 80.7–82.8 dB(A), difference 2.1 dB
Inside 81.7 dB(A) vs outside 49.3 dB(A): 32.4 dB difference (target over 30 dB)
500 Hz to 2 kHz: 30.1 to 32.2 dB difference
All criteria met

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