Pink Noise: Swept
The Swept Pink Noise Block generates a pink noise signal and passes it through a 1/3-octave band-pass filter to limit the spectrum of the output. Before starting a sweep, the center frequency of the band-pass filter tracks the Manual Frequency. The center frequency also returns to the Manual Frequency setting once a sweep stops. The frequency sweep settings determine the range and resolution of the sweep, and how much time the center frequency remains at each frequency setting during the sweep. The output is adjustable to control the volume of the pink noise signal.
Use the Swept Pink Noise block to excite a room at different frequencies to detect rattles in ceilings, walls, appliances, and ductwork. This block is also useful for quickly testing the output of each driver in a multi-way loudspeaker.
- Click the Processing tab to open the Processing Workspace.
- In the palette area, click the DSP tab.
- Expand the Misc: level, delay, meter... category of blocks.
- Click and drag the Pink Noise: Swept block into your Processing Map.
- Wire the output from the Pink Noise: Swept block to the appropriate block.
- (Optional) Customize the names of the block and the output node by clicking their current name and then typing the custom name in the text box that appears. Click the X to save the name.
- Open the Swept Noise block's properties by double-clicking the block or hovering and clicking the properties icon that appears in the upper right of the block's title bar. From here, do the following:
- Unmute the block and use the Manual Frequency and Amplitude settings to set the desired volume for room excitation.
- Determine the frequency range over which you want to check for rattles and use the Start Frequency and Stop Frequency controls to limit the pink noise band-pass sweep. The sweep proceeds logarithmically from the Start Frequency to the Stop Frequency. It pauses for the specified Dwell Time at each of the Steps.
- Use the Start button to start the sweep and listen for rattles. If you hear a rattle, click the Pause button and track down the source of the rattle. If you do not have time to listen everywhere in the room during a single sweep, check the Repeat checkbox so that the sweep restarts automatically when the Stop Frequency is reached. Stop the sweep at any time and return to the Manual Frequency by clicking the Stop button.
note: Pink noise sweeping stops when you disconnect from HAL. The block reverts to the Manual Frequency.
- View the Sweep Progress bar which displays a visual representation of the Sweep settings.
- View the Output meter which indicates the pink noise signal’s rms and peak amplitudes in dBFS and dBr.
note: The Pink Noise: Swept block is muted by default.
| UI Element | Purpose |
|---|---|
| Output node | Connection point for wiring the pink noise output |
(Hover over the thumbnail below to view the properties dialog box.)
| UI Element | Purpose |
|---|---|
|
Sweep Progress |
A visual representation of the Sweep configuration. When connected, the current frequency is displayed in real time. |
| Manual Frequency |
Manual control for setting the frequency of the pink noise. Use in combination with Amplitude to set the desired volume for room excitation. Range is 20 Hz to 20000 Hz. Default = 1000 Hz |
| Amplitude |
Specifies the amplitude of the pink noise output. Use in combination with Manual Frequency to set the desired volume for room excitation. Range is -100 dBr to 0 dBr. Default = -20 dBr |
| Start Frequency |
Specifies the starting frequency for the pink noise band-pass sweep. Range is 20 Hz to 19998 Hz. Default = 20 Hz |
| Stop Frequency |
Specifies the stop frequency for the pink noise band-pass sweep. Range is 22 Hz to 20000 Hz. Default = 20000 Hz |
| Steps |
Range is 1 to 255. Default = 100 |
| Dwell Time |
Specifies the time over which the pink noise sweep pauses between Steps. Range is 10 milliseconds to 2 seconds. Default = 20 milliseconds |
| Control Buttons |
Use these buttons to Start, Stop, and Pause the sweep. |
| Repeat |
When checked, causes the sweep to restart automatically when the Stop Frequency is reached. Default = Unchecked |
| Output (Meter) | Indicates the pink noise signal’s rms and peak amplitudes in dBFS and dBr |
| Mute |
Mutes the block's output Default = Checked (muted) |
See Also