Buying guide for Best sound level meters
Most people are unaware that, in many instances, once hearing damage has occurred it cannot be fixed. There are devices that allow you to compensate, and permanent implants are a possibility, but that’s all a bit extreme. Prevention, as they say, is better than cure, and a good sound level meter can help you protect your hearing, among other uses.
A sound level meter can be used to help resolve a neighborhood noise dispute or protect employees’ hearing in the workplace. While these meters are usually easy to operate, the variety of different models and the features they offer can be quite bewildering.
Key considerations
How it works
Sound can be described as a pressure wave caused by the vibration of an object. If everything were completely still, there would be absolute silence.
A sound level meter (SLM) uses a microphone containing a sensitive diaphragm to measure changes in the air pressure. The information is converted to an electrical signal, interpreted by a microprocessor, and delivered to a display. A sock, or windshield, usually covers the end of the microphone to take out extraneous wind noise, though it can be removed if necessary.
These meters go by many other names, too, such as sound pressure level meters, decibel meters, noise level meters, and noise dosimeters. While there may be a few physical differences, they all do pretty much the same job. Most are handheld, and a few can be mounted on the wall to monitor noise continuously.
Virtual SLMs: There are a few virtual sound level meters around — software programs that can be used on a laptop, tablet, or smartphone. The main issue here is the quality of the microphone, which usually isn’t great and can result in poor readings. One of these can be a very cheap alternative (and at least one is free), but the accuracy of the measurements is questionable unless an external microphone is fitted. If you’re going to do that, you’d probably be better off getting a real sound level meter!
A personal noise dosimeter attaches to clothing and is used to check accurate exposure rates for an individual. However, this type of equipment is expensive, with kits starting at over $1,500.
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Features
Ranges
There are two ranges to consider: loudness in decibels (dB, dBA, or dBC) and frequency in hertz (Hz).
The decibel range is generally from 30 to 130 decibels, which covers everything from quiet conversation to aircraft engines). The frequency is between 30 and 8,500 hertz (usually expressed as 8.5 kilohertz). More advanced models might split those into high and low ranges, thus providing greater accuracy.
Accuracy
Accuracy is a key issue, and it’s a common question (see the FAQ section). The resolution of the display is usually in 0.1 increments both for decibels and frequency, though that doesn’t necessarily signify that the meter itself is capable of that accuracy.
In a nutshell, sound level meters separate into two categories: general-purpose models that homeowners, teachers, and businesspeople might use, and professional models that are made to recognized standards and can be used in commercial and/or legal situations. If you need any kind of proof of sound levels, it’s important you get the latter, which conforms to either American National Standards Institute (ANSI) Type 1 or 2.
Connectivity
Some of the better sound level monitors have USB connectivity, which means that data can be shared with other devices and saved to them for recordkeeping or later processing.
Display
Most sound level meters have a clear digital LCD, usually backlit to allow for working in low-light situations. It’s worth taking a moment to look at the function buttons to see if their purpose is obvious and they’re easy to operate. Sometimes multiple presses are required to access certain data, which can be frustrating, though they don’t usually take long to learn.
Size
Although weight isn’t really a consideration with these devices, physical size may be. Very few of these units are particularly large, but some are more compact than others. That will be useful if you want to carry one in a pocket.
Battery
The battery life is worth considering. A few are rechargeable, but most take AAA or 9-volt batteries that need swapping out. It’s always worth keeping a spare set handy. A power-saving feature is a nice extra — it turns the machine off to save battery life if it’s left unattended.
Case
It’s also nice to get some kind of case to protect the meter.
Did You Know?
OSHA says you should wear ear protection for sounds over 85 decibels. A gas lawn mower is around 90 decibels. However, the Centers for Disease Control and Prevention (CDC) says that consistent exposure to sounds over 70 decibels can lead to some hearing damage.
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Sound level meter prices
Inexpensive: The cheapest sound level meters, often called decibel meters, can be found for around $20. If you just want quick readings of ambient noise, they serve a purpose, though the accuracy is always debatable.
Mid-range: Better quality instruments with a wider range of functions start at around $50, and you can expect to pay $100 to $200 for a recognized Type 2 model.
Expensive: High-precision Type 1 models run anywhere from $250 to $400, and if you need an National Institute of Standards and Technology (NIST) certificate of traceability, you’ll pay at least another $50.
The National Institute for Occupational Safety and Health (NIOSH) offers a free sound level meter app for smartphones. Unfortunately, it’s only available for iOS.
Terms
- Frequency: This is given in hertz (Hz) and is the oscillation of a sound wave in times per second. Most people hear anywhere from 20 to 20,000 hertz, though in some cases frequencies outside this range can still damage your hearing.
- Decibels: The normal way to measure sound level is using decibels (dB). However, this takes into account all sound, including high frequencies you can’t hear, such as the sound bats make, and low frequencies, such as wind (we hear the effect it has on leaves, paper, and so on, but not the wind itself).
- A-weighting: To give a more accurate representation of what the human ear can hear, what’s called an A-weighting is applied. As a result, you’ll see noise levels given as dBA, not just dB.
- C-weighting: This is also available from some models (dBC). It’s useful for low-frequency noise, such as that produced by large engines and some machinery.
- Lavg and Leq: Decibels give a one-off reading, but in commercial or planning situations it’s often necessary to have an average over a specific time frame. Sound level meters that provide this data use either Lavg (the average sound level at slow time weighting), which is the system preferred in the United States, or Leq (equivalent sound level), the system preferred in Europe.
- Weighting: You probably noticed the phrase “slow time weighting” in the previous point. It originated back when meters had an analog needle and dial display. A fast needle would move rapidly due to tiny variations in sound, making reading difficult. A slow needle was damped so it didn’t jump about so much. Today, a slow time weighting is a reading taken over a second; a fast time weighting takes the reading in 125 milliseconds.
- Maximum and minimum: These are easy enough to understand, but fast or slow time weightings might be applied, so several variations are possible. Peak might seem to be the same as maximum, but it has neither fast, slow, nor A-weighting applied, so it’s actually a little higher.
FAQ
Q. How accurate are sound level meters?
A. If you’re using one for compliance purposes, there are two standards regulated by the American National Standards Institute (ANSI): Type 2 (or Class 2), which is accurate to ± 2 decibels, and Type 1 (Class 1), which is accurate to ± 1 decibel. The very best offer NIST traceability, which means they are certified to those standards.
A number of cheap general-purpose sound level meters don’t qualify for either class. Accuracy of ± 1.5 decibels is frequently quoted, though true accuracy may not be that good. Smartphone apps that rely on the phone’s internal microphone can be particularly inaccurate — off by anywhere from 4 to 10 decibels — but when paired with an external mic can meet Type 2 standards.
Q. Do I need to calibrate my sound level meter?
A. It depends on the accuracy you need. If you’re just taking quick readings for personal use, it isn’t necessary. For readings that have any legal or compliance bearing, you should do a field calibration before taking measurements. You’ll need a calibrator that fits over the microphone of your meter. Prices for these start at around $100.
Q. What are the legal regulations concerning noise levels?
A. When you’re at home doing DIY jobs or working in the garage or garden, there are no official regulations, though obviously, it makes sense to look after your hearing. In commercial situations, you need to comply with guidance from the United States Department of Labor Occupational Health and Safety Administration (OHSA). There’s an introductory page about noise exposure here.
