Common Acoustic Measurement Issues and Noise Countermeasures in Anechoic Chambers and Anechoic Boxes

Common Acoustic Measurement Issues and Noise Countermeasures in Anechoic Chambers and Anechoic Boxes
Anechoic chambers and anechoic boxes are designed to isolate external noise and provide a controlled environment for accurate acoustic measurements.
However, to ensure precise results, proper attention must also be given to equipment placement, cable management, and instrument calibration.
This guide outlines common noise-related issues in these environments—and how to resolve them.

Common Noise Sources in Anechoic Testing

Environmental noise within the measurement space

• Electronic noise from the measuring instruments themselves
• Electromagnetic interference (EMI) through cables
• Reflected sound from unintended objects inside the chamber

Cable-Related Noise Problems

• Power cables introducing electrical noise into audio signals
• Audio cables picking up external electromagnetic noise
• Poor cable routing or bundling causing interference

Noise Countermeasures

Environmental Optimization

• Apply sound-absorbing materials to walls, ceilings, and floors to suppress unwanted reflections
• Remove any non-essential objects from the chamber that may cause reflections
• Use separate cable ports (penetration holes) for power and signal lines to minimize interference

Cable Management Solutions

• Use shielded twisted-pair audio cables
• Attach ferrite cores to cables to reduce high-frequency EMI
• Physically separate power and audio signal lines
• Avoid bundling cables; keep cable lengths to the minimum necessary
  Long cables can increase susceptibility to induced noise—shorter is better

Power Noise Suppression

• Use an isolation transformer to eliminate ground loop and AC line noise
• Plug equipment into filtered power strips
• Ensure proper grounding to drain unwanted currents
• Where possible, use battery-powered devices to eliminate AC noise influence

Minimizing Equipment-Induced Noise

• Disable or avoid wireless functions (Wi-Fi, Bluetooth) during measurement
• When using an anechoic box, keep measurement devices outside the enclosure when possible
• Limit use of non-essential devices inside the chamber to reduce reflections
• Ensure instruments are calibrated prior to testing; uncalibrated devices can introduce both noise and measurement error

Pre-, During-, and Post-Measurement Checklist

Before Measurement

• Measure background noise (K1) to verify ambient conditions
• Separate power and signal cables completely, using dedicated cable ports
• Apply ferrite cores to minimize cable noise
• Confirm calibration of all instruments

During Measurement

• Monitor data in real time for anomalies
• Avoid unnecessary movement or vibration that could affect stability
• Evaluate influence of the power supply and use additional filters if needed

After Measurement

• Analyze collected data for potential noise contamination
• Document all measurement conditions for reproducibility
• If noise is detected, identify the source and implement improvements for future measurements

Maximizing the Accuracy of Anechoic Measurements

While anechoic chambers and boxes significantly enhance acoustic measurement quality, improper handling of equipment or cables can still introduce unexpected noise.
By implementing the countermeasures above, you can make full use of your testing environment and achieve highly reliable acoustic data.

If you’re experiencing measurement noise, take the time to review each element of your setup—small changes can make a big difference.

• << Local Exhaust System for Semi-Anechoic Chambers
• Anechoic Chamber and Auxiliary Equipment >>