PannerNode.rolloffFactor - Web APIs 编辑

The rolloffFactor property of the PannerNode interface is a double value describing how quickly the volume is reduced as the source moves away from the listener. This value is used by all distance models.The rolloffFactor property's default value is 1.

Syntax

var audioCtx = new AudioContext();
var panner = audioCtx.createPanner();
panner.rolloffFactor = 1;

Value

A number whose range depends on the distanceModel of the panner as follows (negative values are not allowed):

"linear"

The range is 0 to 1.

"inverse"

The range is 0 to Infinity.

"exponential"

The range is 0 to Infinity.

Exceptions

RangeError

The property has been given a value that is outside the accepted range.

Example

This example demonstrates how different rolloffFactor values affect how the volume of the test tone decreases with increasing distance from the listener:

const context = new AudioContext();
// all our test tones will last this many seconds
const NOTE_LENGTH = 4;
// this is how far we'll move the sound
const Z_DISTANCE = 20;

// this function creates a graph for the test tone with a given rolloffFactor
// and schedules it to move away from the listener along the Z (depth-wise) axis
// at the given start time, resulting in a decrease in volume (decay)
const scheduleTestTone = (rolloffFactor, startTime) => {
  const osc = new OscillatorNode(context);

  const panner = new PannerNode(context);
  panner.rolloffFactor = rolloffFactor;

  // set the initial Z position, then schedule the ramp
  panner.positionZ.setValueAtTime(0, startTime);
  panner.positionZ.linearRampToValueAtTime(Z_DISTANCE, startTime + NOTE_LENGTH);

  osc.connect(panner)
     .connect(context.destination);

  osc.start(startTime);
  osc.stop(startTime + NOTE_LENGTH);
};

// this tone should decay fairly quickly
scheduleTestTone(1, context.currentTime);
// this tone should decay slower than the previous one
scheduleTestTone(0.5, context.currentTime + NOTE_LENGTH);
// this tone should decay only slightly
scheduleTestTone(0.1, context.currentTime + NOTE_LENGTH * 2);

After running this code, the resulting waveforms should look something like this:

Specifications

Browser compatibility

BCD tables only load in the browser

See also

• Using the Web Audio API
• Web Audio spatialisation basics