The new ANSI standard for bandpass filters
Ludwig W. Sepmeyer, Alan H. Marsh · The Journal of the Acoustical Society of America · 1986
The initial American standard for bandpass filters for analysis of sound or vibration was prepared by a Working Group of the Acoustical Society of America's Standards Committee S1 on Acoustics and was approved in 1966 as American National Standard ANSI S1.11-1966. The 1966 standard was re-affirmed in 1976 without technical changes. With advances in microelectronics and digital data-processing techniques available in the 1980s, it was decided in 1981 that a thorough revision of the 1966 Standard was needed. In 1986, the new ANSI Standard was published as ANSI S1.11-1986 with specifications for both analog and digital implementations of octave-band and fractional-octave-band filters including devices that utilize discrete-Fourier-transform techniques to synthesize fractional-octave-band filters. This paper describes the principal technical features of the new standard including the specification of filter design Order Number, Type Number based on error in the analysis of a white noise signal, and a Subtype designation based on error in the analysis of signals having specified positive and negative slopes. Errors are determined relative to the equivalent power that would have been transmitted by an ideal filter having infinite rejection at frequencies outside the range of specified passband-limiting frequencies. Examples are shown to demonstrate how various filter designs would conform to the specifications of the new Standard.