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# getCenterFrequencies

Center frequencies of filters

## Syntax

``cf = getCenterFrequencies(obj)``

## Description

example

````cf = getCenterFrequencies(obj)` returns the center frequencies of the filters created by `obj`, in Hz.```

## Examples

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Create a `gammatoneFilterBank` and get the center frequencies of the filters in the filter bank.

```gammaFiltBank = gammatoneFilterBank; cf = getCenterFrequencies(gammaFiltBank) ```
```cf = 1.0e+03 * Columns 1 through 7 0.0500 0.0822 0.1180 0.1581 0.2027 0.2525 0.3080 Columns 8 through 14 0.3700 0.4390 0.5161 0.6020 0.6979 0.8048 0.9241 Columns 15 through 21 1.0571 1.2054 1.3709 1.5555 1.7613 1.9909 2.2470 Columns 22 through 28 2.5327 2.8513 3.2066 3.6030 4.0451 4.5381 5.0881 Columns 29 through 32 5.7015 6.3857 7.1488 8.0000 ```

Center frequencies of a gammatone filter bank are spaced evenly on the ERB scale. Convert the center frequencies vector to the ERB scale and calculate the differences between center frequencies.

```diff(hz2erb(cf)) ```
```ans = Columns 1 through 7 1.0116 1.0116 1.0116 1.0116 1.0116 1.0116 1.0116 Columns 8 through 14 1.0116 1.0116 1.0116 1.0116 1.0116 1.0116 1.0116 Columns 15 through 21 1.0116 1.0116 1.0116 1.0116 1.0116 1.0116 1.0116 Columns 22 through 28 1.0116 1.0116 1.0116 1.0116 1.0116 1.0116 1.0116 Columns 29 through 31 1.0116 1.0116 1.0116 ```

Create an `octaveFilterBank` and get the center frequencies of the filters in the filter bank.

```octFiltBank = octaveFilterBank; cf = getCenterFrequencies(octFiltBank) ```
```cf = 1.0e+04 * Columns 1 through 7 0.0032 0.0063 0.0126 0.0251 0.0501 0.1000 0.1995 Columns 8 through 10 0.3981 0.7943 1.5729 ```

Center frequencies of an octave filter bank are spaced evenly on a logarithmic scale. Convert the center frequencies vector to the log scale and calculate the differences between center frequencies.

```diff(log10(cf)) ```
```ans = Columns 1 through 7 0.3000 0.3000 0.3000 0.3000 0.3000 0.3000 0.3000 Columns 8 through 9 0.3000 0.2967 ```

Create an octave bandwidth `splMeter` and get the center frequencies of the octave filter bank. Round the center frequencies to two significant digits for display purposes.

```SPL = splMeter('SampleRate',44100,'Bandwidth','1 octave'); cf = getCenterFrequencies(SPL); round(cf,2,'significant') ```
```ans = Columns 1 through 6 32 63 130 250 500 1000 Columns 7 through 10 2000 4000 7900 16000 ```

## Input Arguments

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Object to get filter bank center frequencies from, specified as an object of `gammatoneFilterBank`, `octaveFilterBank`, or `splMeter`.

## Output Arguments

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Filter bank center frequencies in Hz, returned a scalar or vector.