Introduction to Monitoring Noise and Sound
Noise can be defined as the presence of unwanted sound. Something that makes a sound must pulse the air back and forth, generating sound waves detectable by the human ear (in the range of about 20Hz to 20,000 Hertz). These "sound waves" strike our ear drums, which are moved by the changes in air pressure and enable us to perceive sound. Many workplace environments can be harmful, sometimes causing permanent damage, to our hearing.
How Does a Noise Meter Work?
Sound waves are measured using a microphone and converted into data which is displayed and/or logged into memory.
Sound and Noise General Information
Various dB levels and the corresponding reduction in actual sound pressure as well as the human perceived volume reduction for reducing noise levels.
qB Levels
| dB | Actual Sound Pressure Reduction | Perceived Volume Reduction |
|---|---|---|
| 3 dB | 50.00% | 18.77% |
| 6 dB | 75.00% | 34.02% |
| 9 dB | 87.50% | 46.41% |
| 12 dB | 93.75% | 56.47% |
| 15 dB | 96.88% | 64.64% |
| 18 dB | 98.44% | 71.28% |
| 21 dB | 99.22% | 76.67% |
| 27 dB | 99.80% | 84.61% |
| 33 dB | 99.95% | 89.85% |
| 39 dB | 99.99% | 93.30% |
| 45 dB | 100.00% | 95.58% |
| 51 dB | 100.00% | 97.08% |
| 57 dB | 100.00% | 98.08% |
| 63 dB | 100.00% | 98.73% |
| 69 dB | 100.00% | 99.16% |
| 75 dB | 100.00% | 99.45% |
| 81 dB | 100.00% | 99.64% |
OSHA Exposure Limits
Common sources of sound with typical decibel levels and OSHA exposure limits:
| Maximum Exposure per | Sound Level | db | Examples |
|---|---|---|---|
| No Sound | 0 | Threshold of hearing; essentially no sound. | |
| 10 | Breathing. | ||
| Very Quiet | 20 | Whisper, rustling leaves. | |
| Quiet | 50 | Quiet suburb, private office. | |
| Annoying | 70 | Freeway traffic at 50 feet, vacuum cleaner. | |
| Loud | 80 | Garbage disposal, average factory, noisy office. | |
| 8 Hours | 90 | Power drill, shop tools, disel truck. | |
| 2 Hours | Very Loud | 100 | Jet takeoff 1000 feet, outboard motor, tactor. |
| 0 Hours | Pain Threshold | 120 | Loud thunderclap, typical live rock music. |
| Hearing Damage | 125 | Pneumatic riveter at 4 feet. | |
| Permanent Hearing Damage | 132 | Very loud rock concert, 50 feet in front of speaker. | |
| Eardrum Rupture | 150 | Jet takeoff at 75 feet. | |
| Immediate | 180 | Jet engine at 1 foot. | |
| 194 | Loudest sound in air, air particle distortion. |
