What is the sound level meter used for? What methods are used?
Set up the sound level meter before measuring
Setting up a sound level meter before starting a measurement project will save you time and even avoid rework. Here are seven things to remember when checking a sound level meter before starting a project:
Check the time on the sound level meter
During most measurements, events relevant to the report are logged, usually with a watch or mobile phone recording the event time. It is very important that the time on the sound level meter matches your time meter so that your notes will match the recording on the sound level meter. This becomes especially important when using two or more sound level meters.
Set up logging and reporting cycles
Some standards and regulations specify specific measurement intervals. If your sound level meter supports recording at multiple time intervals (referred to as recording and reporting periods on Brüel & Kjær sound level meters), please consider setting the reporting period as required by the standard and the recording period should be shorter in time. This way, you have both the convenience of directly measuring the values required for reporting and the ability to investigate and correct short-term disturbances. This will make it easier for you to start writing reports.
Check if you have enough datastore available
This is a very basic point, so it's easy to forget: remember to check that there is enough free space on the memory card for the upcoming measurement. It is good practice to periodically delete old measurement data after safe download and storage, as is keeping a spare memory card and sound level meter.
set recording
Recordings can be important when post-processing measurement data to identify noise or perform detailed analysis such as FFT-based tonal evaluation. If your sound level meter supports recording, be sure to set it to measure at the correct resolution and sample rate for your needs. It is worth noting that audio recorded with automatic gain cannot be used for subsequent analysis.
Setting Frequency Weighting and Bandwidth for Frequency Analysis
It is best to ensure that you measure the correct frequency weighting and bandwidth for frequency analysis. While it is common practice to post-weight the spectrum, or combine 1/3 octave bands into 1/1 octave bands, both have potential pitfalls. Post-weighting can produce significant errors when there are strong tones far from the center frequency. While summing 1/3 octave bands works for Leq data, it doesn't work for many other parameters like statistics or even Lmax or Lmin.
Turn extended bass on or off
Measuring with an extended low frequency range can increase the impact of wind-induced noise in your measurements, especially those noises that use Z-frequency weighting. Therefore, only extended low frequencies are included when very low frequency noise is relevant.
In addition to the checks that should be performed on a sound level meter before taking measurements, there are a few accessories that are almost always necessary:
A field calibrator is probably the most important accessory for this job. For almost all measurement standards, it is necessary to calibrate the sound level meter before and after each measurement series.
You should always use a microphone windscreen for outdoor measurements. When using a windshield, make sure the sound level meter is corrected for its effect on the measurement. Some sound level meters can automatically detect and correct the windshield.
Use a tripod so your body or movements don't disrupt the soundstage. Use a good quality tripod to hold the microphone or the sound level meter with the microphone attached. If the microphone is connected to the sound level meter by a cable, use an extension pole to ensure correct measurements and to ensure that you or your tripod will not interfere with the measurement.
You'll often need to take measurements in unfamiliar locations, and some locations, such as undeveloped construction sites, may not even have an address, just coordinates. Carrying a handheld GPS device or smartphone can help you find the survey site - and is a better way to record the location of the survey. Sound measurements are meaningless if you don't even know where to measure them!
Many sound level meters come with some form of built-in note-taking capability, but pen and paper are still used to take notes or draw during measurements. The survey form can also provide essential reminders for tasks such as pre- and post-survey calibration checks.
Photos are often required to document your measurement setup, so a camera or smartphone is very important. Photos are essential if anyone wants to repeat measurements.
When making measurements of road traffic noise, you may need to know the number of cars. In this case, you should carry an automatic traffic counter or a hand-held manual counter.
Sound levels can vary greatly depending on the distance from the sound source or reflecting surfaces. These distances can be measured using a tape measure or a laser range finder to ensure that the sound level meter or microphone is in the correct position.
This may seem like a no-brainer, but be sure to charge the battery the day before you're out on the job, and remember to bring a spare rechargeable battery pack. Make sure you have mains power with you if you expect to be away for longer than a normal working day.
For nighttime surveys, you need to know where you are going and what you are doing to prevent injury and make life easier. The headlamp frees your hands.
While surveying the field, you may need to clarify specifications or have questions that need to be answered. Phone numbers and contact information for key personnel are invaluable for getting work done.
warm clothing, food and drink
When taking measurements outdoors, stay comfortable in all weather conditions. Check the weather forecast and remember to pack gloves, rain gear, a hat, boots, thermal socks, sunscreen and insect repellant. Plus, you'll need food, snacks, and drinks to keep you energized. When you're out for a while, the heat from a cup of coffee can keep you energized throughout the day.
