The following tutorials require the Macromedia Flash Player plug-in installed in your browser.

If you cannot visualize this sample movie, the Flash Player plug-in must be downloaded here (installer for Windows) or here (automatic installer inside the browser)

1

Program mode and use

Configuration

Topics covered

Scope and impulse response window are opened and a loopback measurement is performed. The impulse is windowed and its FFT is computed. It is shown how to display the full spectrum range. The actual resolution due to data window length can be observed in the lower part of the spectrum: a longer data window leads to a better frequency resolution.

2

Program mode and use

Configuration

Topics covered

A loudspeaker impulse response is loaded. The anechoical part is already windowed (this information is contained in the file). The FFT of the anechoical part is computed and shown. Different data windowing are shown. The Spectrum Overlay function is used to save different spectra

3

Program mode and use

Configuration

Topics covered

A loopback impulse response is loaded. Time data are wrapped to the right using post processing functions. A portion of data is windowed using the Full Blackman-Harris weighting window. The FFT of selected data is plotted. The effect on the spectrum of changings in the time data window position and length are shown. The spectrum is flat in narrow band. The spectrum is shown in 1/3 octave: each successive band increments of 1 dB in amplitude with frequency. A time domain pink filtering is applied to the impulse response: the 1/3 octave bands now have the same amplitude. The FFT plot is shown again in narrow band: the spectrum shows a constant decrease of 3 dB/octave. Data window is moved to show the effect in the frequency domain. An inverse time domain pink filtering is applied to the impulse response: the spectrum becomes flat again

4

Program mode and use

Configuration

Topics covered

- Selection of a 1000 Hz pure tone in signal generator.

- Scope plot and synchronous sampling of the signal.

- FFT of the data windowed in scope plot.

- Effect of different window lengths and types.

- Harmonic distortion in FFT plot.

5

Program mode and use

Configuration

Topics covered

How to load a WAV file as scope (and not as impulse response) is shown. A WAV file containing a 1 kHz pure tone is loaded. Its spectrum is computed using different data window lengths and types, in narrow-band and 1/3 octave modes.

6

Program mode and use

Configuration

Topics covered

A 2 channels impulse response file is loaded. The spectra of selection A and selection B are shown in 2 different FFT windows. Channel assignment to selections A and B are shown.

7

Program mode and use

Configuration

Topics covered

1) A loopback mesurement is performed. The input level is too high. The distortion leads to many spikes in the time domain, instead than to a clean impulse.

2) the input level is lowered and the loopback mesurement is repeated. The new measurement shows a perfectly clean impulse response.

8

Program mode and use

Configuration

Topics covered

- The sample rate of the soundcard has been fixed at 44.1 kHz.

- When the sample rate in Sample Champion is 44.1 kHz the measured impulse response is clean and still (OK).

- The sample rate in Sample Champion is set at 48 kHz, while the sample rate of the soundcard is still fixed at 44.1 kHz. Now the measured impulse and scope move because of the resampling alghorithms of the sound card drivers.

SOUNDCARD INTERNAL SAMPLE RATE AND SAMPLE CHAMPION SAMPLE RATE MUST BE ALWAYS THE SAME!

9

Program mode and use

Configuration

Topics covered

Settings required for RTA measurement. 1 kHz pure tone has been selected as signal generator. Check of real-time measurement of the input signal in the scope window. Frequency analysis of real-time sampled data in the RTA window, in narrow band and 1/3 octave (repeat mode). Average mode is enabled: the background noise in the FFT spectrum decreases at each successive sampling cycle.

10

Movie describing the above screen capture.

Click here to view the movie.

After clicking press F11 to view full screen, if required.
After finished press ALT+F4 to close the movie window.

11

Program mode and use

Configuration

Topics covered

A 256K samples long room impulse response has been loaded.. The room acoustics plugin is opened. Schroeder plot is shown and ISO 3382 acoustical parameters are computed.

12

Program mode and use

Configuration

Topics covered

Manual selection of a portion of the Schroeder plot and computation of Reverberation Time on a limited decay range.

13

Program mode and use

Configuration

Topics covered

1) A loopback mesurement is performed in repeat mode. The impulse is clean and its spectrum perfectly flat.

2) A noise (music and words) is mixed to the input signal and a new loopback mesurement is performed in repeat mode. The disturbing signal can be seen in the scope window and in the spectrum.

3) The average mode is enabled and a new loopback mesurement is performed: the disturbing signal is attenuated at each successive mesurement cycle.

14

Program mode and use

Configuration

Topics covered

Procedure for automatic latency calibration. Buffer and MLS are set at the same length. The latency calibration is disabled and a loopback measurement is performed. The peak shows a displacement due to hardware and software delays. The automatic latency calibration procedure is then applied and a second loopback measurement is performed. Now the peak is located at t = 0.

15

Program mode and use

Configuration

Topics covered

The procedure for manual latency calibration is shown.

16

Program mode and use

Configuration

Topics covered

Step by step procedure for amplitude calibration. A loopback connection and the internal signal generator are used. A similar procedure is required when an external calibrator is used. The system is calibrated for a 94 dB pure tone. The calibration is verified in the RTA window. Narrow band, 1/3 octave and 1/1 octave frequency data are plotted. The real-time measured peak at 1 kHz shows an amplitude value of 94 dB (+/- 0.01dB)

17

Program mode and use

Configuration

Topics covered

Waterfall analysis of a loudspeaker impulse response

18

Program mode and use

Configuration

Topics covered

A loudspeaker impulse response is loaded. The frequency content of the anechoical part is shown in different ways (spectrum, phase wrapped and unwrapped, Nyquist plot, Energy Time Curve) in the Enhanced View Plugin. A room impulse response is loaded. The spectrogram of the room impulse response is computed and plotted. A comparison between the spectrogram and the simple time data plot is shown.

19

Program mode and use

Configuration

Topics covered

The cross-correlation function in RTA window is shown. The effect has been obtained by means of a real-time measurement of an MLS signal generated by Sample Champion, played by a loudspeaker and sampled synchronously by two microphones. One microphone was kept still while the other has been moved. The displacement of the peak of the cross-correlation function gives information about the time delay between the signals.

20

Movie describing the above screen capture.

Click here to view the movie.

After clicking press F11 to view full screen, if required.
After finished press ALT+F4 to close the movie window.

21

Program mode and use

Configuration

Topics covered

Time data of channel 1 and channel 2 are plotted in an XY graph, generating the classic Lissajous figures. This effect has been obtained by means of a real-time measurement of a 1 kHz tone generated by Sample Champion, played by a loudspeaker and sampled synchronously by two microphones. The first microphone has been kept still while the other has been moved, in order to obtain a phase difference between the signals.

22

Movie describing the above screen capture.

Click here to view the movie.

After clicking press F11 to view full screen, if required.
After finished press ALT+F4 to close the movie window.

23

Program mode and use

Configuration

Topics covered

The correlation meter function in RTA window is shown. The effect has been obtained by means of a real-time measurement performed on a 1 kHz tone generated by Sample Champion, played by a loudspeaker and sampled synchronously by two microphones. The first microphone has been kept still while the other has been moved, in order to obtain a phase difference between the signals.

24

Movie describing the above screen capture.

Click here to view the movie.

After clicking press F11 to view full screen, if required.
After finished press ALT+F4 to close the movie window.

25

Movie showing a loudspeaker measurement example.

Click here to view the movie.

After clicking press F11 to view full screen, if required.
After finished press ALT+F4 to close the movie window.

26

Loopback configuration.

Movie showing 2 measurement cases:

Synch REC/PLAY (MLS ON): - Signal shown in the X4 USB soundcard's VU-meters
- Impulse peak on the upper plot
- MLS signal on the lower plot

REC only (MLS OFF): - No signal shown in the X4 USB soundcard's VU-meters
- Random noise on the upper plot (with autoscale ON)
- No signal on the lower plot

When there is no signal on input, the computed impulse response will be noise.

Click here to view the movie.

After clicking press F11 to view full screen, if required.
After finished press ALT+F4 to close the movie window.