sweeptone

Exponential swept sine

Syntax

excitation = sweeptone()

excitation = sweeptone(swDur)

excitation = sweeptone(swDur,silDur)

excitation = sweeptone(swDur,silDur,fs)

excitation = sweeptone(___,Name,Value)

Description

excitation = sweeptone() returns an excitation signal generated using the exponential swept sine (ESS) technique. By default, the signal has a 6-second duration, followed by 4 seconds of silence, for a sample rate of 44100 Hz.

excitation = sweeptone(swDur) specifies the duration of the exponential swept sine signal.

excitation = sweeptone(swDur,silDur) specifies the duration of the silence following the exponential swept sine signal.

excitation = sweeptone(swDur,silDur,fs) specifies the sample rate of the sweep tone as fs Hz.

excitation = sweeptone(___,Name,Value) specifies options using one or more Name,Value pair arguments, in addition to the input arguments in the previous syntaxes.

Examples

Estimate Impulse Response Using Sweep Tone Excitation

Create a sweep tone excitation signal by using the sweeptone function.

excitation = sweeptone(2,1,44100);

plot(excitation)
title('Excitation')

Pass the excitation signal through an infinite impulse response (IIR) filter and add noise to model a real-world recording (system response).

[B,A] = butter(10,[.1 .7]);
rec = filter(B,A,excitation);
nrec = rec + 0.12*randn(size(rec));

plot(nrec)
title('System Response')

Pass the excitation signal and the system response to the impzest function to estimate the impulse response. Truncate the estimate to 100 points. Use impz to determine the true impulse response of the system. Plot the true impulse response and the estimated impulse response for comparison.

irEstimate = impzest(excitation,nrec);
irEstimate = irEstimate(1:101);

irTrue = impz(B,A,101);
plot(0:100,irEstimate, ...
     0:100,irTrue,'ro')

legend('True impulse response','Estimated impulse response')

Generate ESS Signal

Generate an exponential swept sine (ESS) signal with a 3-second sweep that goes from 20 Hz to 20 kHz, and ends with a 2-second silence. Specify the sample rate as 48 kHz.

fs = 48e3;
excitation = sweeptone(3,2,fs,'SweepFrequencyRange',[20 20e3]);

Visualize the excitation in time and time-frequency.

t = (0:numel(excitation)-1)/fs;
plot(t,excitation)
xlabel('Time (s)')

spectrogram(excitation,512,0,1024,fs,'yaxis')

Input Arguments

swDur — Duration of exponential swept sine signal (s)

6 (default) | scalar in the range [0.5,15]

Duration of exponential swept sine signal in seconds, specified as a scalar in the range [0.5,15].

The total duration of the excitation signal must be less than or equal to 15 seconds: swDur + silDur ≤ 15.

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

silDur — Duration of silence after exponential swept sine signal (s)

4 (default) | scalar in the range (0,14.5]

Duration of silence after exponential swept sine, specified as a scalar in the range (0,14.5].

The total duration of the excitation signal must be less than or equal to 15 seconds: swDur + silDur ≤ 15.

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

fs — Sample rate (Hz)

44100 (default) | positive scalar

Sample rate in Hz, specified as a positive scalar.

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

Name-Value Pair Arguments

Specify optional comma-separated pairs of Name,Value arguments. Name is the argument name and Value is the corresponding value. Name must appear inside quotes. You can specify several name and value pair arguments in any order as Name1,Value1,...,NameN,ValueN.

Example: 'ExcitationLevel',-5

'ExcitationLevel' — Level of excitation signal to generate (dB)

-6 (default) | scalar in the range [-42,0]

Level of the excitation signal to generate in dB, specified as a scalar in the range [-42,0].

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

'SweepFrequencyRange' — Range of sweep frequency (Hz)

[10 22000] | two-element positive row vector

Range of sweep frequency in Hz, specified as a two-element row vector. The sweep frequency range can be specified low to high or high to low. That is, [10 22000] and [22000 10] are both valid inputs. The largest value of the sweep frequency range must be less than or equal to fs/2.

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

Output Arguments

excitation — Excitation signal

column vector

Excitation signal generated using the ESS technique, returned as a column vector. The length of the column vector is approximately (swDur+silDur)*fs samples.

Data Types: double

References

[1] Farino, Angelo. "Advancements in Impulse Response Measurements by Sine Sweeps." Presented at the Audio Engineering Society 122nd Convention, Vienna, Austria, 2007.