The getFrequencyResponse() method of the IIRFilterNode interface takes the current filtering algorithm's settings and calculates the frequency response for frequencies specified in a specified array of frequencies.

The two output arrays, magResponseOutput and phaseResponseOutput, must be created before calling this method; they must be the same size as the array of input frequency values (frequencyArray).


IIRFilterNode.getFrequencyResponse(frequencyArray, magResponseOutput, phaseResponseOutput);


A Float32Array containing an array of frequencies, specified in Hertz, which you want to filter.
A Float32Array to receive the computed magnitudes of the freqency response for each frequency value in the frequencyArray.
A Float32Array to receive the computed phase response values in radians for each frequency value in the input frequencyArray.

Return value



The three arrays provided are not all of the same length.


In the following example we are using an IIR filter on a media stream (for a complete full demo, see our stream-source-buffer demo live, or read its source.) As part of this demo, we get the frequency responses for this IIR filter, for five sample frequencies. We first create the Float32Array objects we need, one containing the input frequencies, and two to receive the output magnitude and phase values:

var myFrequencyArray = new Float32Array(5);
myFrequencyArray[0] = 1000;
myFrequencyArray[1] = 2000;
myFrequencyArray[2] = 3000;
myFrequencyArray[3] = 4000;
myFrequencyArray[4] = 5000;

var magResponseOutput = new Float32Array(5);
var phaseResponseOutput = new Float32Array(5);

Next we create a <ul> element in our HTML to contain our results, and grab a reference to it in our JavaScript:

<p>IIR filter frequency response for: </p>
<ul class="freq-response-output">
var freqResponseOutput = document.querySelector('.freq-response-output');

Finally, after creating our filter, we use getFrequencyResponse() to generate the response data and put it in our arrays, then loop through each data set and output them in a human-readable list at the bottom of the page:

var feedforwardCoefficients = [0.1, 0.2, 0.3, 0.4, 0.5];
var feedbackCoefficients = [0.5, 0.4, 0.3, 0.2, 0.1];

var iirFilter = audioCtx.createIIRFilter(feedforwardCoefficients, feedbackCoefficients);


function calcFrequencyResponse() {
  iirFilter.getFrequencyResponse(myFrequencyArray, magResponseOutput, phaseResponseOutput);

  for(i = 0; i <= myFrequencyArray.length-1;i++){
    var listItem = document.createElement('li');
    listItem.innerHTML = '<strong>' + myFrequencyArray[i] + 'Hz</strong>: Magnitude ' + magResponseOutput[i] + ', Phase ' + phaseResponseOutput[i] + ' radians.';



Specification Status Comment
Web Audio API
The definition of 'getFrequencyResponse()' in that specification.
Working Draft

Browser compatibility

ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
getFrequencyResponseChrome Full support 49Edge Full support 14Firefox Full support 50IE No support NoOpera Full support 36Safari ? WebView Android Full support 49Chrome Android Full support 49Firefox Android Full support 50Opera Android Full support 36Safari iOS ? Samsung Internet Android Full support 5.0


Full support
Full support
No support
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Compatibility unknown
Compatibility unknown

See also