A or C Frequency Weightings? The human ear responds more to frequencies between 500 Hz and 8 kHz and is less sensitive to very low-pitch or high-pitch noises. The frequency weightings used in sound level meters are often related to the response of the human ear, to ensure that the meter is measuring what you actually hear. It is extremely important that sound level measurements are made using the correct frequency weighting – usually A-weighting. For example, measuring a tonal noise of around 31 Hz could result in a 40 dB error if using C-weighting instead of A-weighting. A Weighting The most common weighting that is used in noise measurement is A-Weighting. It follows the frequency sensitivity of the human ear at low levels. This is the most commonly used weighting scale, as it also predicts quite well the damage risk of the ear. Sound level meters set to the A-weighting scale will filter out much of the low-frequency noise they measure, similar to the response of the human ear. Noise measurements made with the A-weighting scale are designated dBA. C Weighting The response of the human ear varies with the sound level. At higher levels 100 dB and above, the ear’s response is flatter. The C-weighting scale is quite flat, and therefore includes much more of the low-frequency range of sounds than the A Although the A-Weighted response is used for most applications, C-Weighting is also available on many sound level meters. C Weighting is usually used for Peak measurements and also in some entertainment noise measurement, where the transmission of bass noise can be a problem. Extech SL510 Sound Level Meter Features: ±1dB high accuracy meets Class 2 standards (IEC 61672-2013 and ANSI/ASA S1.4/Part 1) A & C Weighting Backlit LCD to view in dimly lit areas Data Hold and Min/Max functions Auto power off with disable Tripod mount (optional TR100 Tripod sold separately) Complete with microphone wind-screen, wrist strap, and three AAA batteries Extech SL510 Sound Level Meter Specifications: Specifications Range Range 35 to 130dB Basic Accuracy ±1dB @ 1KHz Resolution 0.1dB Weighting A & C Response Time Fast/Slow Microphone Electret condenser 0.5″ (12.7mm) Dimensions 167x45x20mm Weight 160g
