Overview
ISO 9614-1:1993 - "Acoustics - Determination of sound power levels of noise sources using sound intensity - Part 1: Measurement at discrete points" - specifies a standardized method to determine the sound power radiated by a noise source by measuring the normal component of sound intensity on a hypothetical surface enclosing the source. Measurements are taken at discrete points (one-octave or one‑third‑octave bands) and used to compute octave, one‑third‑octave or band‑limited A‑weighted sound power levels. The method is applicable in situ or in special test environments for sources with stationary noise and a physically definable measurement surface.
Key topics and requirements
- Measurement principle: Sound power is obtained by integrating the normal sound intensity over a surface that fully encloses the source - i.e., summing partial sound powers from discrete surface segments.
- Frequency ranges: One‑third‑octave band measurements are supported in practice from about 50 Hz to 6.3 kHz; one‑octave band data commonly from 63 Hz to 4 kHz. A‑weighted values are calculated from band results, not measured directly.
- Instrumentation & probes: Use of calibrated sound intensity probes and instrumentation compliant with IEC/ISO requirements; attention to probe orientation and dynamic capability.
- Acoustic environment: The method tolerates more realistic (less restricted) test conditions than pressure‑based standards but requires stationarity of the source and control of extraneous noise and airflow (effects covered in annexes).
- Quality indicators & uncertainty: The standard defines grades of accuracy (e.g., precision, engineering, survey) and ancillary tests (annex B) and field indicators (annex A) used to assess measurement quality and estimate uncertainty.
- Practical considerations: Guidance on installation, surface segmentation, measurement positions, and factors that bias results (airflow, absorption within the measurement surface - annexes C and D).
Applications and who uses it
- Acoustical consultants and test laboratories performing in situ sound power determinations of machinery and installations.
- Manufacturers and product engineers measuring noise emissions of large or installed equipment that cannot be tested in anechoic or calibrated reverberant rooms.
- Environmental noise assessors and occupational hygienists evaluating sound power for noise control, compliance, and mitigation design.
- Use cases include field measurement of compressors, motors, HVAC systems, industrial machinery and other sources where traditional pressure‑based laboratory methods are impractical.
Related standards
- ISO 9614 (Part 2: measurement by scanning)
- ISO 3740–3747 series (pressure‑based sound power methods)
- IEC 1043 (instruments for sound intensity)
- ISO 5725 (precision of test methods)
Keywords: ISO 9614-1:1993, sound intensity measurement, sound power levels, measurement at discrete points, in situ acoustics, one‑third‑octave, A‑weighted sound power.
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