Is Android sound meter app accurate?
Sound meters are devices used to measure sound pressure levels in decibels (dB). They have a microphone to detect sound waves and convert them into an electrical signal that can be displayed and analyzed. Sound meters are commonly used in various applications like occupational noise assessments, environmental noise monitoring, product testing, and noise ordinance enforcement.
With the proliferation of smartphones, many sound measurement apps have been developed that use the built-in microphone to measure sound levels. However, the microphones in phones are designed for voice calls rather than precision sound level measurements. This brings into question the accuracy of mobile sound meter apps compared to dedicated professional-grade sound level meters.
How Sound Meters Work
Sound is measured in decibels (dB), which are units that compare the sound pressure level to a reference value. The quietest sound a human can hear is at 0 dB, while 120-140 dB is the threshold for pain. Sound meters use a microphone to convert sound waves into an electrical signal that can be analyzed to determine the sound level in dB.
According to How decibel sound level meters work, sound meters have several key components:
- Microphone – Detects sound waves and converts them into voltage signals
- Preamplifier – Amplifies the electrical signal from the microphone
- Filtering – Removes unwanted noise frequencies
- Detector – Measures the filtered signal and determines the sound level
- Display – Shows the sound level reading in dB
By processing the electrical signal and filtering out noise, sound meters can provide an accurate measurement of the sound level, even in noisy environments. The reading is shown on the display, usually in the standard weighted decibel units of dBA or dBC.
Accuracy Testing Methodology
In order to test the accuracy of Android sound meter apps, researchers need to establish a controlled testing environment and benchmark equipment to compare the app readings against [1]. This allows them to minimize variables and isolate the performance of the app.
A typical accuracy testing methodology involves using a professional grade sound level meter as the benchmark. The sound level meter is calibrated and known to provide accurate decibel measurements. The smartphone running the sound meter app is placed right next to the professional meter and measurements are taken simultaneously in a controlled environment [1].
Testing is usually conducted in a specialized acoustic chamber that allows researchers to control the sound source and environment. Standard frequencies and decibel levels are generated and measured by both devices [2]. This allows the app readings to be compared directly to the calibrated sound level meter benchmark for accuracy.
Test Results
Several studies have tested the accuracy of popular Android sound meter apps compared to professional-grade sound level meters. One NIOSH study tested SoundMeter and SoundLevel Meter and found they were accurate to within ±1 dB when a calibrated external microphone was used (https://blogs.cdc.gov/niosh-science-blog/2014/04/09/sound-apps/). Another study by Cirrus Research tested six apps (including Decibel X, Noise Meter, and NoiSee) and found most were accurate to 2 dB or better with a suitable external mic (https://www.cirrusresearch.co.uk/blog/2021/10/sound-level-meter-apps-accuracy/).
However, accuracy varied more when using only built-in smartphone microphones. A Reddit user found their smartphone decibel meter app was off by 5-10 dB compared to a professional meter (https://www.reddit.com/r/audioengineering/comments/qa5va5/how_accurate_are_smartphone_decibel_meter_apps/). Factors like microphone quality, calibration, and proper setup impact accuracy.
In summary, tests show popular Android sound apps can achieve professional-grade accuracy under controlled conditions with an external mic. But built-in smartphone mics often reduce accuracy to ±5 dB or worse.
Factors Affecting Accuracy
There are several factors that can affect the accuracy of sound measurements taken with smartphone apps. Two key factors are microphone quality and calibration.
Most smartphones have basic microphones designed for telephone calls and voice recordings, not precise sound measurements. The quality and sensitivity of these built-in microphones can vary significantly between different phone models and manufacturers. Higher quality measurement microphones can greatly improve accuracy, but add to the device cost and complexity (1).
Proper calibration is also essential for achieving accurate, consistent results. Smartphone microphones should be calibrated against known reference sound sources. However, most free or inexpensive sound meter apps do not allow user calibration. More advanced apps may provide a calibration function, but it requires additional hardware. Without periodic calibration, measurement drift can occur over time (2).
In one study, an iPhone app recorded noise levels around 2 dB higher after the phone was repaired, likely due to microphone replacement during servicing. This demonstrates the impact device changes can have on calibration (3). Careful calibration procedures and consistent testing methodology are necessary for reliable measurements.
Tips for Improving Accuracy
There are a few techniques you can use to improve the accuracy of sound measurements from your Android phone:
Use an external microphone. The built-in microphone on your phone can pick up interfering noises and may not have a flat frequency response. An external calibrated microphone connected to the audio input jack greatly improves accuracy.
Calibrate your phone’s mic against a reliable reference sound meter. You can do this by placing both meters side by side and exposing them to the same sound source. Adjust your phone meter’s settings until it matches the reference meter. This helps account for microphone variances.
Avoid interference by shielding your phone mic from wind and other ambient noises. Cases or DIY barriers like foam can isolate the primary sound source.
Take multiple measurements and average the results to smooth out any anomalies or spikes.
Select an app that allows input sensitivity adjustment and calibration. This gives you more control over the measurement process.
With some tweaking and calibration, smartphone sound meters can achieve results accurate enough for most casual hobbyist uses. For professional-grade measurements, invest in dedicated sound level meters.
When Good Enough is Enough
While professional grade sound level meters are necessary for legal compliance and standardized measurements, in many casual use cases, a basic indication of sound levels is sufficient. For applications like getting a rough idea of ambient noise levels at home or detecting louder versus quieter locations, precision down to the decibel may not be required.
Smartphone sound meter apps can provide a good enough general sense of sound levels for informal personal use. As an Audioholics article points out, “Technical measurements are demonstrably precise, repeatable events. Hearing perception is not.” (1) In other words, human hearing doesn’t detect sound with scientific precision anyway. So for casual contexts, being in the ballpark is often adequate.
Additionally, factors like background noise, reflection, and microphone inconsistencies have less impact for directional assessments like identifying noisier rooms or times of day. While the specific decibel readings may be off, the relativity between higher and lower volumes is still discernible. For many everyday applications, smartphone sound measurement apps provide sufficient accuracy.
The Bottom Line
Based on tests conducted by NIOSH researchers and discussions on Reddit forums, the accuracy of Android sound meter apps can vary greatly depending on the specific app used and testing methodology. Apps that utilize internal smartphone microphones often lack the sensitivity and calibration needed for professional-grade sound level measurements. However, apps that leverage external calibrated microphones can reach accuracy levels similar to dedicated sound level meters according to NIOSH tests.
While apps using internal microphones may not be reliable enough for OSHA compliance testing or other official purposes, they can provide ballpark measurements for general sound level checks. Factors like microphone sensitivity, calibration, background noise, and proper use technique affect accuracy. With the right app choice and methodology, Android sound meter apps can be accurate enough for informal personal use cases.
Expert Recommendations
Based on accuracy testing, experts recommend using the NIOSH SLM app for iPhone or Decibel X for Android as the most accurate free sound measurement apps. These apps provide professional-grade sound level meter functionality and can reliably measure ambient noise levels and loudness of specific sources.
For casual everyday use, apps like Decibel 10th and Sound Meter are reasonably accurate and easy to use. They work well for getting a general sense of environmental noise levels. However, for occupational safety testing, legal cases, or other situations requiring precision, NIOSH SLM or Decibel X are advised.
It’s important to understand these apps have limitations. Factors like microphone quality, calibration, and how you hold your phone can impact accuracy. For official compliance testing, always use a certified sound level meter. But for personal use, smartphone apps can provide valuable noise level measurements within a few decibels of accuracy.
The Future of Mobile Sound Measurement
The future of mobile sound measurement apps looks promising with emerging technologies like AI processing and built-in calibration to improve accuracy. A study by Fox et al (2022) found that AI can analyze sound data combined with sensor data like location to better identify noise sources and filter ambient noise. This may allow future sound measurement apps to provide measurements isolated to a specific noise source, ignoring irrelevant ambient sounds (https://canadianaudiologist.ca/feature-4/). Additionally, built-in calibration using reference microphones and pre-tested hardware can help correct individual device inconsistencies. Murphy (2016) showed that custom calibration improved accuracy significantly compared to uncalibrated smartphones, bringing mobile measurements much closer to lab-grade meters (https://www.sciencedirect.com/science/article/abs/pii/S0003682X15003667). While regulatory use still requires dedicated equipment, AI and calibration may soon make mobile sound apps reliable enough for many common uses.
