Can you measure noise with Android phone?

With the proliferation of smartphones, using these devices for audio measurements and analysis is becoming increasingly popular. Smartphones contain microphones and other sensors that can capture and analyze sound and noise. While professional sound level meters remain the most accurate tool for measuring noise, smartphones provide an accessible and low-cost alternative.

This article will provide an overview of using Android smartphones to measure environmental noise levels. We’ll look at the basics of noise measurement, the capabilities of smartphone hardware, available noise measurement apps, techniques for capturing accurate readings, and the limitations of using a phone compared to a professional sound level meter.

Noise Measurement Basics

Sounds are vibrations that travel through the air as mechanical waves. They are created when objects vibrate and produce pressure variations that move through a medium like air or water (Inceusa, n.d.).

Noise refers to unwanted or unpleasant sounds that disrupt or interfere with normal activities. It is usually measured on a decibel (dB) scale that indicates the loudness or intensity of the sound. Noise above certain levels can be annoying, distracting, and even damaging to hearing (Epd.gov.hk, n.d.).

While noise is often subjective, some common sources of unwanted sound include vehicle engines, construction equipment, airplane takeoffs, loud music, and noisy neighbors. Environmental noise pollution from human activities is a growing concern in many urban areas.

Noise Measurement Units

When measuring noise, the most common unit used is the decibel (dB). Decibels are used to quantify sound intensity or loudness. The decibel scale is logarithmic, meaning a 10 dB increase represents a 10 times increase in sound intensity. As explained by E-Noise Control, the logarithmic nature of the decibel scale allows it to encompass the enormous range of sound intensities the human ear can detect.

There are a few key metrics when it comes to reporting noise levels in decibels:

dB(A) – A-weighted decibels, which adjusts measurements to account for the varying sensitivity of human hearing at different frequencies.
dB(C) – C-weighted decibels, which focuses on low frequency sounds.

dB(Z) – Z-weighted decibels, which does not apply any weighting and measures the full frequency spectrum.

According to Pulsar Instruments, dB(A) is the most common metric used for environmental noise measurements and occupational noise exposure regulations.

Noise Level Guidelines

Several organizations provide guidelines and regulations for acceptable noise levels in various environments. According to the World Health Organization (WHO) Occupational Noise Exposure – Overview, noise levels above 85 dB over an 8 hour period may lead to permanent hearing loss. The WHO recommends less than 70 dB over 24 hours to prevent hearing loss.

The Occupational Safety and Health Administration (OSHA) regulates occupational noise exposure in the United States. OSHA mandates that employers implement a hearing conservation program when workers are exposed to 85 dB over an 8 hour work shift 1910.95 – Occupational noise exposure. The noise measurements integrate sound levels from 80 dB to 130 dB.

The Environmental Protection Agency (EPA) provides guidelines for community noise levels. The EPA states that to protect public health, noise levels should not exceed 70 dB over 24 hours. For indoor residential areas, the EPA recommends no more than 45 dB during daytime hours and 35 dB at night.

Smartphone Hardware Capabilities

When it comes to using a smartphone to measure noise levels, the key hardware components are the microphone(s) and speakers. Most modern smartphones contain multiple microphones to help with noise cancellation during calls as well as to enable certain software features. For example, the iPhone 13 contains a total of 5 microphones.

The quality of the microphones in smartphones has improved dramatically over the years. According to one source, the iPhone 6 microphone is capable of measuring sounds up to 120 dB, with an accuracy of +/- 5 dB in the 40-100 dB range (1). However, microphone quality can vary across different smartphone models and brands. Professional sound level meters are capable of measuring up to 140 dB with high accuracy.

In addition to microphone hardware, the speakers in a smartphone play an important role. Most sound measurement apps require emitting a test tone from the speakers in order to calibrate the microphone input. The frequency response of the speakers affects the accuracy of calibration and measurement.

Lastly, software plays a critical role in enabling smartphone noise measurement capabilities. The built-in OS audio APIs, audio processing algorithms, and custom apps determine how well a smartphone can capture, analyze, and report on noise levels.

(1) https://canadianaudiologist.ca/feature-4/

Noise Measurement Apps

There are a number of apps available for Android phones that can measure noise levels using the built-in microphone. Some of the most popular and highly-rated options include:

Sound Meter – Allows you to measure ambient noise in dB with A, B, and C frequency weightings. Provides average and peak level readings.

NoiseAlert – Measures sound levels and alerts you when decibels exceed harmful levels. Can run in the background to monitor noise exposure over time.

Decibel 10th – Features proprietary calibration for improved accuracy. Logs noise data over time and maps noise levels.

These apps leverage the built-in microphone on Android phones to measure sound levels in dB. Features like frequency weighting, calibration, data logging over time, and mapping provide added functionality beyond just spot checking noise levels.

Using Smartphones to Measure Noise

Measuring noise levels with a smartphone is a straightforward process. Here are the basic steps:

Download a sound measurement app from your phone’s app store. There are many free and paid options, like Sound Meter, Decibel X, and Noise Meter.

Allow the app to access your microphone when prompted.
Open the app and point your phone’s microphone toward the noise source. Make sure nothing is blocking the mic.
The app will display the decibel (dB) measurement of the noise. Many apps show the instant reading as well as minimum, maximum and average levels.

To get an accurate measure, take readings from multiple positions and average the results.
For ongoing noise monitoring, most apps can log and export data over time. Useful for assessing noise throughout the day.
Compare the noise levels to guidelines for residential, commercial or workplace limits to determine if they are excessive.

With a good app and careful methodology, smartphones can measure noise quite accurately. However, professional-grade equipment provides more consistent and precise measurements.

Accuracy Limitations

While smartphones can be used to measure noise levels, they have some important accuracy limitations to consider. The microphones built into smartphones are designed for voice calls and recordings, not specialized acoustic measurement. As a result, their frequency response and sensitivity may not be optimized for measuring environmental noise levels.

According to a 2016 study published in Applied Acoustics, iOS noise measurement apps tend to overestimate true noise levels by an average of 2.93 dB(A), while Android apps underestimate by an average of -3.01 dB(A) [1]. This suggests smartphone microphones should not be relied upon for precise, professional-grade noise level monitoring without proper calibration and testing.

To improve accuracy, measurement apps need to be calibrated properly against a known reference sound source. However, variations between individual smartphone microphones mean that apps may need recalibrating if changing between different devices. Environmental factors like temperature and accessory microphones can also impact readings.

While smartphone noise measurement has convenience benefits, results should be considered rough estimates. For professional acoustic monitoring and compliance testing, purpose-built sound level meters with calibrated microphones remain the most accurate tool.

Use Cases for Measuring Noise with a Smartphone

Some common use cases for measuring noise levels with a smartphone include:

Workplace noise – Employees can check if noise levels in different areas of a workplace exceed occupational noise exposure limits set by OSHA (Occupational Safety and Health Administration). For example, noise near heavy machinery or construction equipment.

Concerts and events – Attendees can test noise levels at concerts, sports events, bars, and clubs. This helps determine appropriate hearing protection needs. Many venues have decibel levels exceeding 120dB, where hearing damage can occur.(1)

Neighborhood noise – Residents can measure noise from nearby construction, traffic, or other loud disturbances. This provides objective data if filing a noise complaint.(1)

Personal exposure – People can test noise levels in daily life, like commuting or using headphones. This identifies listening habits that may put your hearing at risk.(2)

Classroom noise – Teachers can track ambient noise during different classroom activities. High decibel levels make it hard for students to hear instructions.(1)

Conclusion

To summarize, recent advances in smartphone hardware and software have enabled limited noise level measurements using the built-in microphone and specialized apps. Smartphones can provide rough estimates of ambient noise levels, with accuracy varying greatly based on the specific device capabilities and measurement app used, typically within ±5-10 dB. While not as accurate as dedicated sound measurement equipment, smartphone-based noise measurements offer a convenient and accessible alternative for certain casual use cases. Measurements should be interpreted with the limitations in mind, and results validated through comparative measurements when higher accuracy is needed.

Looking to the future, noise measurement capabilities on smartphones will likely continue improving as hardware improves. Wider adoption would enable crowd-sourced noise mapping and monitoring on an unprecedented scale. However, accuracy limitations may remain challenging. Further research and innovation focused on improving measurement accuracy and capabilities specifically for smartphones would enable more reliable use cases. Overall, smartphones have potential to democratize basic noise measurement and monitoring, complementing traditional equipment.