Are sound meter apps reliable?

Sound meter apps are software designed to utilize a smartphone’s built-in microphone to measure surrounding noise levels (Kardous & Shaw, 2014). They display real-time sound pressure readings in decibels (dB) and are commonly used for noise monitoring in occupational, environmental, and recreational settings. The intended uses of sound meter apps include assessing potential noise hazards, monitoring personal noise exposure, and gathering noise data for research or compliance purposes. With their convenience and accessibility, these apps aim to place professional-grade sound level meter functionality on consumer devices.

How Sound Meter Apps Work

Sound meter apps turn your smartphone into a sound level meter by using the built-in microphone to measure decibel levels. The app records the sound pressure and converts it into a decibel reading using algorithms. Many apps can measure a wide range of frequencies from very low bass to high pitched sounds. The apps display the instantaneous sound level as well as the maximum and minimum levels over a period of time. Some advanced apps even provide frequency spectrum analysis.

Accuracy Compared to Dedicated Sound Meters

Professional-grade sound level meters are designed specifically to measure noise levels accurately. They contain high-quality microphones and components calibrated to pick up sounds within certain frequencies. However, consumer smartphone microphones have some limitations in comparison.

According to a study by the CDC’s National Institute for Occupational Safety and Health (NIOSH)(1), many smartphone apps can provide rough estimates of loudness, but few achieve the accuracy of a dedicated sound level meter. The built-in microphones on phones tend to be optimized for voice calls rather than precise noise measurements.

Factors like microphone placement and operating temperature also impact measurement. Professional meters allow calibration and customized set-up to control for environmental factors. Overall, dedicated sound meters remain the most accurate tool for scientific-grade noise measurement.

Factors Affecting Reliability

There are several factors that can affect the reliability and accuracy of measurements from sound meter apps:

One major factor is the microphone quality differences between phones. Smartphone microphones are not designed or calibrated specifically for accurate sound level measurements. The microphones can vary greatly in sensitivity and frequency response between different phone models ¹. This makes it difficult to compare readings between different devices or achieve consistency.

Background noise and echoing can also impact the readings. The microphone picks up all ambient sounds, not just the direct source being measured. So loud background noise or sounds reflecting off walls and objects can contaminate the measurements ². This reduces reliability when trying to isolate a specific noise source.

Other factors like microphone placement and orientation, operating temperature, and the testing environment also play a role. Overall, smartphone microphones lack the sophistication for professional-grade sound measurements.

Using Sound Meter Apps Effectively

To use sound meter apps more reliably:

First, take multiple readings instead of relying on a single reading. Sound levels can fluctuate, so taking 3-5 readings and looking at the average value will provide a more accurate result. Taking readings from different locations can also help account for differences based on where you position your phone.

It’s also important to calibrate and test the app before fully depending on its readings. Apps may need to be calibrated based on your specific phone model. You can test calibration by measuring a known sound source, like conversational speech at 60-70 dB. Compare the app’s readings to this expected range. If the values are off, the app may need calibration for optimal accuracy.

Additionally, look at reviews and technical specifications to choose apps that use professional-grade calibration methods. Avoid apps that don’t disclose calibration techniques.

With proper use practices and choosing quality-controlled apps, sound level meter apps can provide approximate guidance on environmental noise levels. However, critical applications may still require dedicated professional sound level meters for maximum precision.

Typical Use Cases

Sound meter apps have a few common use cases that take advantage of having a decibel meter readily available on a smartphone. Two typical examples include:

General Noise Level Checks

One of the most common uses for sound meter apps is to quickly check ambient noise levels. For instance, you can test the decibel levels in different rooms of a house, office, restaurant or other location. This allows you to identify particularly loud or quiet areas. According to one source, normal conversation is around 60 dB, while loud traffic can exceed 85 dB and harm hearing over time (1).

Identifying Loud Household Appliances

Sound meter apps can also help identify which household appliances produce the most noise. You can walk around your home and take decibel readings near appliances like the fridge, microwave, blender or laundry machines. This allows you to pinpoint devices that may disrupt sleep or conversations. One study found that many blenders produce noise over 90 dB up close (2).

Limitations to Keep in Mind

While sound meter apps can provide rough estimates of sound levels, they have limitations that prevent them from being reliable enough for professional use.

The microphones and calibration in smartphones are not as accurate as dedicated sound level meters used for professional measurements. Small variances in microphone sensitivity can result in different readings between devices.

According to a study by Canadian Audiologists, the AudioTools app only provided average sound levels over 1 minute intervals, without minimum or maximum values. Professional sound meters capture the full range of sound levels.

Tests by NIOSH found sound apps were within ±1 dB accuracy under controlled conditions, but real-world environmental factors can further decrease accuracy. The study warned apps should not replace professional sound level meters.

Overall, while apps provide ballpark figures, their lack of professional-grade microphones and calibration make them unreliable for situations requiring precise, consistent sound level measurements.

Improving Reliability

There are a few ways to improve the reliability and accuracy of sound meter app measurements:

Use an external high-quality microphone – The built-in microphones in smartphones are generally not optimized for accurate sound measurements. Using a calibrated external microphone designed for sound level measurements can improve accuracy. Look for an external mic that is omnidirectional and meets ANSI or IEC standards for sound level meters. Popular options are the iMM-6 from Dayton Audio and the iMM-7 from AWM.

Take readings close to the source – Positioning the microphone as close as possible to the sound source you want to measure improves reliability. Being too far away increases effects from background noise and reflected sounds. Most guidelines recommend being within 1 foot of the source if possible.

Compare with a dedicated sound level meter – Do a test comparison with a known-accurate handheld sound level meter to check the app’s accuracy under real-world conditions. Look for consistency in readings between the app and sound meter.

Calibrate your smartphone/mic – Some apps have a built-in calibration feature to customize for your specific device. Use a calibrator like the iCAL from Dayton Audio to calibrate and improve accuracy.

Top-Rated Sound Meter Apps

Based on reviews and accuracy testing, some of the top-rated sound meter apps include:

Decibel X (https://thenewyorkhearingcenter.com/2018/01/sound-level-apps-for-smartphones/). This app is considered one of the best free options due to its intuitive interface and reliable results. It measures sound levels from 30 to 130 decibels and provides readable graphs.

SoundMeter by Faber Acoustical (https://www.youtube.com/watch?v=O1vhauINVH0). This paid app calibrates your device’s microphone for accurate sound level measurements within 1-2 dB. It includes options like frequency weighting and integration time.

NIOSH SLM by the National Institute for Occupational Safety and Health (NIOSH) (https://www.cdc.gov/niosh/topics/noise/app.html). Developed by sound experts, this free app measures occupational noise exposure and shows results similar to professional sound level meters.

Conclusion

Sound meter apps can provide a general idea of noise levels and be useful for certain applications, but have significant limitations compared to dedicated professional sound level meters. The microphone in a smartphone is not calibrated and optimized for accurate acoustical measurements, and measurement accuracy can vary widely depending on the specific app, phone model and various environmental factors. There are techniques that can improve reliability, such as using an external calibrated microphone, but in general sound meter apps should not be relied upon when accurate noise level data is critical. The key is being aware of the limitations and potential for inaccurate readings, and only using the apps casually or for applications where precision is not vital. For any usage where legal compliance, health and safety guidelines or other standards must be met, a professional sound level meter is essential. When used appropriately as a general guideline and with proper caution, sound meter apps can be a convenient tool for casual sound level checks.