IIRFilterNode: getFrequencyResponse() method
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since April 2021.
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
).
Syntax
getFrequencyResponse(frequencyArray, magResponseOutput, phaseResponseOutput)
Parameters
frequencyArray
-
A
Float32Array
containing an array of frequencies, specified in Hertz, which you want to filter. magResponseOutput
-
A
Float32Array
to receive the computed magnitudes of the frequency response for each frequency value in thefrequencyArray
. phaseResponseOutput
-
A
Float32Array
to receive the computed phase response values in radians for each frequency value in the inputfrequencyArray
.
Return value
None (undefined
).
Exceptions
NotSupportedError
DOMException
-
Thrown if the three arrays provided are not all of the same length.
Examples
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:
const myFrequencyArray = new Float32Array(5);
myFrequencyArray[0] = 1000;
myFrequencyArray[1] = 2000;
myFrequencyArray[2] = 3000;
myFrequencyArray[3] = 4000;
myFrequencyArray[4] = 5000;
const magResponseOutput = new Float32Array(5);
const 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"></ul>
const 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:
const feedforwardCoefficients = [0.1, 0.2, 0.3, 0.4, 0.5];
const feedbackCoefficients = [0.5, 0.4, 0.3, 0.2, 0.1];
const iirFilter = audioCtx.createIIRFilter(
feedforwardCoefficients,
feedbackCoefficients,
);
// …
function calcFrequencyResponse() {
iirFilter.getFrequencyResponse(
myFrequencyArray,
magResponseOutput,
phaseResponseOutput,
);
for (let i = 0; i < myFrequencyArray.length; i++) {
const listItem = document.createElement("li");
listItem.textContent = `${myFrequencyArray[i]}Hz: Magnitude ${magResponseOutput[i]}, Phase ${phaseResponseOutput[i]} radians.`;
freqResponseOutput.appendChild(listItem);
}
}
calcFrequencyResponse();
Specifications
Specification |
---|
Web Audio API # dom-iirfilternode-getfrequencyresponse |
Browser compatibility
BCD tables only load in the browser