Relevant Test Standards

ISO 3741:2010/ANSI S12.51-2012 – Acoustics – Determination of Sound Power Levels and Sound Energy Levels of Noise Sources using Sound Pressure – Precision Methods for Reverberation Test Rooms

This standard describes the sound measurement method of a source in a highly reverberant space.  All surfaces in the space reflect sound, instead of absorbing sound.  The absorption coefficient of the materials in the reverberant space (on a scale of 0 to 1) must be less than 0.06.  When a sound source is excited, sound pressure level is measured. The standard describes a method for calculating sound power and sound energy levels based on the sound pressure level measurements. The typical frequency range of interest is 100 Hz to 10,000 Hz one-third octave bands, but lower frequencies measured in very large rooms are also considered.

IAC Acoustics Systems design to meet above standard:

• Macrodyne Hardliner Reverberation Room

ISO 3744:2010/ANSI S12.54-2011 – Acoustics – Determination of Sound Power Levels and Sound Energy Levels of Noise Sources Using Sound Pressure - Engineering Methods for an Essentially Free Field Over a Reflecting Plane

ISO 3744:2010 outlines the method for testing a noise source in a free-field near a reflecting plane – hemi-anechoic room.  The noise source measurements are performed by placing microphones in a series of locations specified in the standard, where the placement and number of microphone locations depends on the geometry of the source.  The sound pressure level measurements are used to calculate the sound power, or sound energy, of the source.  The typical frequency range of interest is in the 125 Hz to 8,000 Hz octave bands, or 100 Hz to 10,000 Hz one-third octave bands.

IAC Acoustics Systems design to meet above standard:

• Microdyne Hemi-Anechoic Chambers
• Microdyne Anechoic Chambers
• Moduline Controlled Acoustic Rooms

ISO 3745:2012 Acoustics — Determination of sound power levels and sound energy levels of noise sources using sound pressure — Precision methods for anechoic rooms and hemi-anechoic rooms

ISO 3745:2012 shows a detailed method for measuring sound pressure level in either a hemi-anechoic or anechoic space.  The accuracy of measurements required is higher than with the ISO 3744 measurement method.  To assess the accuracy of the free field in the test space, a sound source is typically placed near the center floor of the room, and measurements are recording at specified distances from the source.   The typical frequency range of interest is 100 Hz to 10,000 Hz one-third octave bands.  Methods for estimating sound energy and sound power levels given a set of sound pressure measurements are described.

IAC Acoustics Systems design to meet above standard:

• Microdyne Hemi-Anechoic Chambers
• Microdyne Anechoic Chambers

ISO 3746:2010 Acoustics – Determination of sound power levels and sound energy levels of noise sources using sound pressure - Survey method using an enveloping measurement surface over a reflecting plane

This ISO standard describes the methodology for measuring the sound pressure level of a noise source.  The sound pressure level measurements are used to calculate the sound power, or sound energy, of the source.  The test environment is not limited to a specific type (i.e., free-field, reverberant field), other than the fact that it contains at least one reflecting plane.  Since the test environment is more generic, a correction factor is applied in accordance with the method listed in Annex A.  The microphone and noise source test setup follows the requirements from ISO 3744:2010.  The typical frequency range of interest is in the 125 Hz to 8,000 Hz octave bands.

IAC Acoustics Systems design to meet above standard:

• Microdyne Hemi-Anechoic Chambers
• Microdyne Anechoic Chambers
• Moduline Controlled Acoustic Rooms

ISO 26101-1:2021 Acoustics – Test Methods for the Qualification of the Acoustic Environment – Part 1: Qualifications of Free-Field Environments

This standard focuses on the acoustic environment exclusively, outlining methods of measurement in both a free field – anechoic chamber- or a free field over a reflecting plane – hemi-anechoic chamber.  The divergence loss method is used.  The measurement method of the free-field environment is similar to, but not exactly the same as, ISO 3745.  It describes how to calculation deviations from the inverse square law, and the spatial distance between microphone measurements is smaller.  The typical frequency range of interest is 100 Hz to 10,000 Hz one-third octave bands.

IAC Acoustics Systems design to meet above standard:

• Microdyne Hemi-Anechoic Chambers
• Microdyne Anechoic Chambers

ISO 7779:2018 Acoustics — Measurement of airborne noise emitted by information technology and telecommunications equipment

This standard focuses on acoustic measurements of IT and telecommunications equipment.  Sound pressure measurements are used at specified locations around the product under test to estimate sound power.  This standard allows measurements in three types of spaces: a free-field environment – anechoic room, a free-field with one reflecting plane – hemi-anechoic room, or a reverberation room.  A variety of test setups are described for various IT and telecommunications products. The typical frequency range of interest is in the 100 Hz to 10,000 Hz one-third octave bands.

IAC Acoustics Systems design to meet above standard:

• Microdyne Hemi-Anechoic Chambers
• Microdyne Anechoic Chambers
• Moduline Controlled Acoustic Rooms
• Macrodyne Hardliner Reverberation Room

ETSI ES 202 396-1 V1.7.1 Speech and Multimedia Transmission Quality (STQ); Speech Quality Performance in the Presence of Background Noise; Part 1: Background Noise Simulation Technique and Background Noise Database

This ETSI standard is frequently used in developing products used for sound recording and playback.  It outlines a test method to measure how well speech is transmitted through electronics audio equipment.  This standard required an acoustic environment with specific, measurable parameters outline in 6.1.  A range of room dimensions, acceptable reverberation times, and a noise floor specification is given.  Sound is recording using an artificial binaural head, and speech intelligibility metrics are used to assess how well speech is identified.  The frequency range of interest is 200 Hz to 8 kHz.

IAC Acoustics Systems design to meet above standard:

• Microdyne Hemi-Anechoic Chambers
• Macrodyne Hardliner VRT Room