getANSICenterFrequencies

Get the list of valid ANSI S1.11-2004 center frequencies

Syntax

centerFrequencies = getANSICenterFrequencies(octFilt)

Description

centerFrequencies = getANSICenterFrequencies(octFilt) returns a vector of valid center frequencies as specified by the ANSI S1.11-2004 standard.

Examples

Get ANSI Center Frequencies

Create an object of the octaveFilter System object™. Call getANSICenterFrequencies to get a list of valid center frequencies.

octFilt = octaveFilter;
centerFrequencies = getANSICenterFrequencies(octFilt)

centerFrequencies = 1×15
103 ×

    0.0005    0.0010    0.0020    0.0040    0.0079    0.0158    0.0316    0.0631    0.1259    0.2512    0.5012    1.0000    1.9953    3.9811    7.9433

Input Arguments

octFilt — Object of octaveFilter

object

Object of the octaveFilter System object™.

Output Arguments

centerFrequencies — Center frequencies

vector

Center frequencies specified by the ANSI S1.11-2004 standard, returned as a vector.

The range for computing valid center frequencies is 3 Hz to (Fs/2) Hz, where the SampleRate property of your octave filter defines Fs.

Data Types: single | double

Algorithms

The ANSI S1.11-2004 standard [1] defines the center frequencies of the octave bands as

$$f_c=\{\begin{array}{ll}{f}_r\times G^{(k-30)/b},\hfill & b\text{ is odd}\hfill \\ f_r\times G^{(2k-59)/2b},\hfill & b\text{ is even}\hfill \end{array}$$

where:

• f_r is the reference frequency, 1000 Hz.

• G is the octave ratio, 10^0.3.

• b is the number of bands per octave, which is the inverse of the bandwidth of the filter in octaves. Specify the bandwidth using the Bandwidth property of octFilt.

• k is any integer and represents the band number.

The center frequency definition differs depending on whether b is odd, such as for bandwidths of 1 octave or 1/3 octave, or even, such as for bandwidths of 1/2 octave or 1/6 octave. This ensures that the band edges of the whole octave band remain band edges for all of the fractional bands.

References

[1] Acoustical Society of America. American National Standard Specification for Octave-Band and Fractional-Octave-Band Analog and Digital Filters. ANSI S1.11-2004. Melville, NY: Acoustical Society of America, 2009.

Version History

Introduced in R2016b