Vernier Software and Technology
Vernier Software & Technology

Sound Level Meter User Manual

Sound Level Meter

The Sound Level Meter measures sound level in decibels. It can be used for activities such as

  • Environmental noise studies
  • Sound level comparisons
  • Investigating room acoustics
  • Sound isolation modeling
  • Sound propagation modeling

Note: Vernier products are designed for educational use. Our products are not designed nor are they recommended for any industrial, medical, or commercial process such as life support, patient diagnosis, control of a manufacturing process, or industrial testing of any kind.

What's Included

  • Sound Level Meter
  • Wind screen (black foam cover for the sensing element)
  • 4 AAA batteries (preinstalled in the meter)
  • Cable to connect the sensor to a data-collection interface (order code CB-SLM)

Compatible Software and Interfaces

The Sound Level Meter may require a compatible interface and software. Choose a platform below to see compatible interface and software options.

Getting Started

  1. Turn the Sound Level Meter on by sliding the Power/Measurement Range Switch to an appropriate measurement range (35–90 or 75–130 dB).
  2. Connect the mini-end plug of the cable to the Sound Level Meter and connect the other end of the cable to the interface (LabQuest Mini, LabQuest 2, etc.).
  3. Start the appropriate data-collection software (Logger Pro, Logger Lite, LabQuest App) if not already running, and choose New from File menu.

The software will identify the sensor and load a default data-collection setup. You are now ready to continue your experiment.

If you are collecting data using a Chromebook™, mobile device such as iPad® or Android™ tablet, or a Vernier wireless sensor or interface, please see the following link for up-to-date connection information:

www.vernier.com/start/slm-bta

Using the Product

The Sound Level Meter functions as a standalone device, and you can monitor sound levels by reading the LCD panel.

If you want to collect sound level data, you need to connect the Sound Level Meter to a data-collection interface. To do so, connect the sensor following the steps in the Getting Started section of this user manual. For most classroom activities, the following settings on the Sound Level Meter work well:

  1. Slide the power switch to the appropriate range.
  2. Set the time weighting switch to S.
  3. Set the maximum level hold switch to RESET.
  4. Set the frequency weighting to A.

For in-depth sound studies, you may need to choose different settings more appropriate for your experiment.

Power/Measurement Range Switch

This slide switch, labeled “O/35–90/75–130,” turns on the sensor and sets the measurement range. When set to the 35–90 range (LO), the sensor is designed to measure sound levels in the range of 35 to 90 dB. When the switch is set to the 75–130 range (HI), the sensor is designed to measure sound levels in the range of 75 to 130 dB. A range warning will appear if the measured sound is beyond the range of the current setting. If this warning appears continuously, set the switch to the appropriate range.

Time Weighting

The S/F switch just below the LCD sets the time weighting. For normal measurements set the switch to the slow setting (S). For fluctuating noise, set the weighting to fast (F). In the classroom, you will probably set it to S.

Maximum Level Hold

Setting the MAX/RESET button to MAX sets the LCD display to show the maximum, weighted sound level. In the classroom you will probably set it to RESET, in which case it will continually display the sampled reading. If you are using the Sound Level Meter without a Vernier interface, you can use the MAX setting to record and display only the loudest sound level. Setting this switch to MAX does not affect the output signal sent to the data-collection interface.

Frequency Weighting

The A/C switch is used to set the weighting scale. A-weighted setting is the sound level value that most closely matches that of the human hearing range. It is the weighting scale most commonly used for Occupational Safety and Health Administration (OSHA) and Department of Environmental Quality (DEQ) regulatory measurements. The C-weighted scale is useful for monitoring sources such as engines, explosions, and machinery. This setting would also be used if you use the Sound Level Meter to get the total unweighted sound level of the noise source. For more details about A vs. C weighting scales, see www.vernier.com/til/3500

The sensor comes with a foam windscreen. The windscreen helps reduce the detection of false high signals caused by wind blowing across the microphone. It also protects the microphone from dust and debris.

Calibration

You should not need to calibrate the Sound Level Meter for classroom use. Calibration is possible, but it will require access to a special calibrator, capable of producing sound at a particular frequency at a pre-determined sound level, not commonly available in the classroom.

Specifications

Sensor

1/2" electret (prepolarized) condenser microphone

Power

Four AAA batteries

Battery life

50 hours typical

Display

3 1/2" LCD

Measurement range

  • Low: 35 to 90 dB
  • High: 75 to 130 dB

Frequency range

31.5 to 8000 Hz

Resolution

0.1 dB

Accuracy

1.5 dB (ref 94 dB @ 1 kHz)

Output

  • DC: 10 mV/dB
  • AC: 1.0 Vrms corresponding to the top of the selected range

Stored calibration

  • Slope: 100 dB/V
  • Intercept: 0 dB/V

How the Sensor Works

The Sound Level Meter uses an electret condenser microphone mounted on the end of a shaft. The output of this microphone is fed into a series of filters, amplifiers, integrators, and adder circuits to produce a single sound pressure level measurement. The Sound Level Meter uses a directional microphone, which requires the instrument to be pointed in the direction of the noise source unless ambient noise levels are being monitored.

Suggested Sound Level Studies

You can collect sound level data in many real-world situations; for example, you can

  • Collect sound levels before, during and after a concert or dance.
  • Collect sound levels throughout the day in a school hallway or shopping mall.
  • Use the Sound Level Meter to judge cheering contests at pep rallies.
  • Collect data outside and inside a car equipped with a stereo system.
  • Make a model of an ear and ear canal. Measure sound levels at the “ear drum” when a headset is placed over the ear. Repeat the experiment but place an earplug between the headset and the meter.
  • Set up the Sound Level Meter to collect readings in a variety of situations. Use the following chart to determine the acceptable duration for exposure to the sound level you measure.

The following chart shows the sound level exposure rates set by the OSHA Occupational Noise Exposure Standard. In a work environment, for example, it is acceptable to be exposed to 90 dB for eight hours as measured on the A-weighted scale. If the sound level is 100 dB, the acceptable duration is two hours.

Duration per day (hrs) Sound level, slow-response (dBA)
8.0 90
6.0 92
4.0 95
2.0 100
1.0 105
0.5 110
0.25 115

Example Sound Levels

Source Sound Pressure Level (dBA)
Large rocket (nearby) 180 to 194
Jet aircraft 150
Shotgun blast 145
Propeller aircraft 140
Pneumatic riveter, threshold of pain 130
Rock concert, thunder 120
Construction noise 110
Subway train 100
Heavy truck 90
Noisy restaurant 80
Busy traffic, normal radio 70
Normal conversation, dishwasher 60
Quiet office 50
Library 40
Soft whisper 30
Rustling leaves 20
Normal breathing 10
Threshold of hearing 0

Standard Octave Band Frequencies Ranges with Corresponding A and C Weighting Values

Center Frequency (Hz) Effective Band (Hz) A Weighting (dB) C Weighting (dB)
31.5 22.1–44.2 –39.4 –3.0
63 44.2–88.4 –26.2 –0.8
125 88.4–177 –16.1 –0.2
250 177–354 –8.6 0
500 354–707 –3.2 0
1000 707–1,414 0 0
2000 1,414–2,828 1.2 –0.2
4000 2,828–5,657 1.0 –0.8
8000 5,657–11,314 –1.1 –3.0

Additional Experiments

For more information about experiments related to this product, see www.vernier.com/slm-bta

Troubleshooting

If your Sound Level Meter is not operating correctly, first check that the batteries are charged and that the Meter turns on. Use the cable to connect the Meter to a Vernier interface and verify that the Sound Level Meter is identified by the data‑collection software. For more troubleshooting tips, see www.vernier.com/til/1386

Repair Information

If you have followed the troubleshooting steps and are still having trouble with your Sound Level Meter, contact Vernier Technical Support at support@vernier.com or call 888-837-6437. Support specialists will work with you to determine if the unit needs to be sent in for repair. At that time, a Return Merchandise Authorization (RMA) number will be issued and instructions will be communicated on how to return the unit for repair.

Accessories/Replacements

Item Order Code

Cable for Sound Level Meter

CB-SLM

Warranty

Vernier warrants this product to be free from defects in materials and workmanship for a period of five years from the date of shipment to the customer. This warranty does not cover damage to the product caused by abuse or improper use. This warranty covers educational institutions only.

Contact Support

Fill out our online support form or call us toll-free at 1-888-837-6437.

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