PannerNode.coneInnerAngle - Web APIs 编辑

The coneInnerAngle property of the PannerNode interface is a double value describing the angle, in degrees, of a cone inside of which there will be no volume reduction.

The coneInnerAngle property's default value is 360, suitable for a non-directional source.

Syntax

var audioCtx = new AudioContext();
var panner = audioCtx.createPanner();
panner.coneInnerAngle = 360;

Value

A double.

Example

In this example, we'll demonstrate how changing the orientation parameters of a PannerNode in combination with coneInnerAngle and coneOuterAngle affects volume. To help us visualise how the orientation vector affects, we can use the Right-hand rule:

First, let's start by writing a utility function to figure out our orientation vector. The X and Z components are always at a 90° to each other, so we can use the sine and cosine functions, which are offset by the same amount in radians. However, normally this would mean the PannerNode points to the left of the listener at 0° rotation – since `x = cos(0) = 1` and `z = sin(0) = 0`. It's more useful to offset the angle by -90°, which means the PannerNode will point directly at the listener at 0° rotation.

// this utility converts amount of rotation around the Y axis
// (i.e. rotation in the 'horizontal plane') to an orientation vector
const yRotationToVector = degrees => {
  // convert degrees to radians and offset the angle so 0 points towards the listener
  const radians = (degrees - 90) * (Math.PI / 180);
  // using cosine and sine here ensures the output values are always normalised
  // i.e. they range between -1 and 1
  const x = Math.cos(radians);
  const z = Math.sin(radians);

  // we hard-code the Y component to 0, as Y is the axis of rotation
  return [x, 0, z];
};

Now we can create our AudioContext, an oscillator and a PannerNode:

const context = new AudioContext();

const osc = new OscillatorNode(context);
osc.type = 'sawtooth';

const panner = new PannerNode(context);
panner.panningModel = 'HRTF';

Next, we set up the cone of our spatialised sound, determining the area in which it can be heard:

// this value determines the size of the area in which the sound volume is constant
// if coneInnerAngle == 30, it means that when the sound is rotated
// by at most 15 (30/2) degrees either direction, the volume won't change
panner.coneInnerAngle = 30;
// this value determines the size of the area in which the sound volume decreases gradually
// if coneOuterAngle == 45 and coneInnerAngle == 30, it means that when the sound is rotated
// by between 15 (30/2) and 22.5 (45/2) degrees either direction,
// the volume will decrease gradually
panner.coneOuterAngle = 45;
// this value determines the volume of the sound outside of both inner and outer cone
// setting it to 0 means there is no sound, so we can clearly hear when we leave the cone
// 0 is also the default
panner.coneOuterGain = 0;
// increase the Z position to ensure the cone has an effect
// (otherwise the sound is located at the same position as the listener)
panner.positionZ.setValueAtTime(1, context.currentTime);

Having set up the PannerNode, we can now schedule some updates to its Y-axis rotation:

// calculate the vector for no rotation
// this means the sound will play at full volume
const [x1, y1, z1] = yRotationToVector(0);
// schedule the no-rotation vector immediately
panner.orientationX.setValueAtTime(x1, context.currentTime);
panner.orientationY.setValueAtTime(y1, context.currentTime);
panner.orientationZ.setValueAtTime(z1, context.currentTime);

// calculate the vector for -22.4 degrees
// since our coneOuterAngle is 45, this will just about make the sound audible
// if we set it to +/-22.5, the sound volume will be 0, as the threshold is exclusive
const [x2, y2, z2] = yRotationToVector(-22.4);
panner.orientationX.setValueAtTime(x2, context.currentTime + 2);
panner.orientationY.setValueAtTime(y2, context.currentTime + 2);
panner.orientationZ.setValueAtTime(z2, context.currentTime + 2);

Finally, let's connect all our nodes and start the oscillator! 

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

osc.start(0);

Specifications

Browser compatibility

BCD tables only load in the browser

See also

• Using the Web Audio API
• Web Audio spatialisation basics