The Bedrock BAC3 is a precision IEC 60942 Class 1 acoustic calibrator generating 94 dB SPL at 1 kHz. It is used for field calibration verification of Class 1 and Class 2 sound level meters before and after each measurement session, in accordance with the requirements of IEC 61672-3, ISO 9612, ISO 1996, and all major sound measurement standards that require calibration checks. Every measurement campaign that will be used for regulatory or contractual purposes requires a documented calibration check with an acoustic calibrator — the BAC3 provides this capability in a compact, reliable instrument.
Field calibration verification with an acoustic calibrator is distinct from laboratory calibration. Laboratory calibration (ISO 17025 accredited) is performed annually or every two years and provides a full traceable calibration certificate. Field calibration verification is performed at the start and end of every measurement session and confirms that the sound level meter reading is within ±0.5 dB of the known calibrator output. If the before and after readings differ by more than 0.5 dB, the measurement session results are considered invalid and must be repeated.
The BAC3 provides a single calibration output at 94 dB SPL / 1 kHz — sufficient for field calibration verification at a single reference level. The BAC4 provides two outputs (94 dB and 114 dB at 1 kHz), enabling calibration verification across a wider dynamic range. For most field measurement applications, the BAC3's single level is sufficient. The BAC4 is preferred when your measurement campaigns span a wide dynamic range and you want to verify linearity at both ends of the measurement range.
The standard field calibration verification procedure with the BAC3 is: (1) Before starting the measurement session, fit the BAC3 onto the sound level meter microphone. (2) Wait 30 seconds for the calibrator output to stabilise. (3) Read the SPL displayed on the instrument and confirm it reads 94.0 dB ± 0.5 dB. (4) Note the reading in your measurement record. (5) Proceed with the measurement session. (6) Repeat the check at the end of the measurement session. (7) If the post-session reading differs from the pre-session reading by more than 0.5 dB, the session results are invalid and must be repeated. Store the BAC3 reading in the project file as part of the measurement record required by ISO 9612, ISO 1996, and other standards.
Request a Quote · BAC4 Multi-Level Calibrator · All Products · Download Datasheet