A,B, and C Contours

Standard filter contours are used to make the instrument more nearly approximate the normal human ear. The different contours were intended to match the ear at different sound intensities. 标准滤波器轮廓用于使仪器更接近正常人类耳朵的特性。不同的轮廓旨在匹配不同声音强度下的耳朵特性。

This is the Weighting control on a research-quality General Radio sound level meter. The weighting marked 20kHz means that it has a certified flat response to 20kHz. Most low-cost sound level meters cannot merit such certification, and typically have just two weightings, A and C. The C weighting is reasonably close to a flat decibel response. 这是科研级通用声级计上的加权控制。标有20kHz的加权表示它已通过认证，对20kHz有平坦的响应。大多数低成本声级计无法获得此类认证，通常只有两种加权，即A和C。C加权相对接近平坦的分贝响应。

A Contour Filter

The A-contour filters out significantly more bass than the others, and is designed to approximate the ear at around the 40 phon level. It is very useful for eliminating inaudible low frequencies. A-contour 滤除的低频显著多于其他类型，其设计目的是在约40 phon电平上近似人耳。它对于消除不可听的低频非常有用。

Sound Measurement in dBA

When making practical assessments of the sound level of a concert or as a part of a general survey of ambient sound levels, the type of measurement which is usually made is that of the level in dBA. This measurement is made with a sound level meter with an A contour filter which provides the best instrument match of the ear's equal loudness curves for soft sounds in the neighborhood of 40 dB. When this filter, (which is one of the standard contour filters of most sound level meters) is used, the levels should be recorded as dBA rather than dB. The unit dB implies that all frequencies in the audible frequency range are treated equally - something very different from what the ear does. A good practice in sound level surveys is to measure all levels in both dBA and in the flat-response mode where the intensity in decibels (dB) is measured directly. Measurements made in dBA approximate the loudness level in phons and are practical to make with a standard meter.

B Contour Filter

The intermediate B-contour aproximates the ear for medium loud sounds. It is rarely used. 中间B轮廓近似表示中等响度声音的耳部特征。它很少被使用。

C Contour Filter

The C-contour does not filter out as much of the lows and highs as the other contours. It approximates the ear at very high sound levels and has been used for traffic noise surveys in noisy areas. C型轮廓在低频和高频部分的滤除效果不如其他轮廓。它在极高声压级下能近似模拟人耳，并已被用于噪声较大的区域的交通噪声调查。