spectrum

HRTF power spectrum

Since R2024a

Syntax

h = spectrum(s)

h = spectrum(s,Name=Value)

[h,f] = spectrum(___)

[h,f,ang] = spectrum(___)

spectrum(___)

Description

h = spectrum(s) returns the power spectrum of the HRTF measurements in the horizontal plane at zero elevation.

h = spectrum(s,Name=Value) specifies options using one or more name-value arguments.

[h,f] = spectrum(___) also returns the frequencies of the spectrum.

[h,f,ang] = spectrum(___) also returns the angles corresponding to the measurements.

spectrum(___) with no output arguments plots the power spectrum.

Examples

Compute Power Spectrum of HRTF Data

Read in a SOFA file containing HRTF measurements.

s = sofaread("ReferenceHRTF.sofa");

Use spectrum to compute the power spectrum of the HRTF data in the horizontal plane at zero elevation for the first receiver.

[h,f] = spectrum(s);

Call spectrum with no output arguments to plot the power spectrum of the HRTF data in the horizontal plane for the first receiver.

spectrum(s)

Compute Power Spectrum of Interpolated HRTF Data

Read in a SOFA file containing HRTF measurements.

s = sofaread("ReferenceHRTF.sofa");

Use spectrum to compute the power spectrum of the HRTF data in the horizontal plane offset by 7 degrees of elevation. See how the returned spectrum is empty because the SOFA file contains no measurements in the specified plane.

h = spectrum(s,Plane="horizontal",PlaneOffsetAngle=7);
size(h)

ans = 1×2

        2048           0

Call spectrum with InterpolateHRTF set to true to compute the spectrum using interpolated HRTF measurements corresponding to 100 uniformly-spaced points in the specified plane.

h = spectrum(s,Plane="horizontal",PlaneOffsetAngle=7,InterpolateHRTF=true);
size(h)

ans = 1×2

        2048         100

Call spectrum with no output arguments to plot the computed spectrum.

spectrum(s,Plane="horizontal",PlaneOffsetAngle=7,InterpolateHRTF=true);

Input Arguments

s — SOFA object

SimpleFreeFieldHRIR object | SimpleFreeFieldHRSOS object | SimpleFreeFieldHRTF object

SOFA object, specified as one of the following objects.

• SimpleFreeFieldHRIR

• SimpleFreeFieldHRSOS

• SimpleFreeFieldHRTF

Name-Value Arguments

Specify optional pairs of arguments as Name1=Value1,...,NameN=ValueN, where Name is the argument name and Value is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

Example: spectrum(s, Plane="median")

Receiver — Indices of receivers

1 (default) | vector of positive integers

Indices of the receivers to use for the power spectrum, specified as a vector of positive integers.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

NPoints — Number of points in spectrum

positive integer

Number of points in the spectrum, specified as a positive integer. For SimpleFreeFieldHRIR objects, the default value is max(2048,L), where L is the length of the HRTF impulse responses. For SimpleFreeFieldHRSOS objects, the default value is 2048.

This argument does not apply to SimpleFreeFieldHRTF objects.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

Plane — Plane

"horizontal" (default) | "median" | "sagittal"

Plane to compute spectrum for, specified as "horizontal", "median", or "sagittal".

Data Types: char | string

PlaneOffsetAngle — Plane offset angle

0 (default) | value in range [-90,90]

Plane offset angle in degrees, specified as a value in the range [-90,90]. This angle specifies the offset by which the Plane is shifted.

This argument only applies to the horizontal and sagittal planes. For the horizontal plane, the offset corresponds to the elevation angle. For the sagittal plane, the offset corresponds to the lateral angle.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

AngleTolerance — Angle tolerance

1 (default) | positive scalar

Angle tolerance in degrees, specified as a positive scalar. The function computes the spectrum of measurements within the tolerance of the plane specified by Plane and PlaneOffsetAngle.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

InterpolateHRTF — Use interpolated HRTF measurements

false (default) | true

Use interpolated HRTF measurements, corresponding to 100 uniformly-spaced points in the specified plane, to compute the power spectrum. Set this argument to true if the plane specified by Plane, PlaneOffsetAngle, and AngleTolerance does not contain a sufficient number of HRTF measurements. The function uses the bilinear interpolation method.

Data Types: logical

Output Arguments

h — Power spectrum

N-by-M-by-R array

Power spectrum computed from the HRTF data, returned as an N-by-M-by-R array, where:

• N is the length of the spectrum.

• M is the number of selected measurements.

• R is the number of selected receivers defined by Receiver.

f — Frequencies

vector of length N

Frequencies in Hz corresponding to the spectrum, returned as a vector of length N, where N is the length of the spectrum.

ang — Angles

vector

Angles in degrees corresponding to the measurements used to compute the spectrum, returned as a vector. The interpretation of the angles depends on the specified Plane.

• For the horizontal plane, the angles correspond to the azimuth.

• For the median plane, the angles correspond to the elevation.

• For the sagittal plane, the angles correspond to the polar angles.

Version History

Introduced in R2024a