Easily create high-quality test tones, sweeps, and audio files to check the phase of your speakers in an instant with this app for Mac OS X.
What is Make a Test Tone?
Make a Test Tone is a sinusoidal audio test signal generator and spoken phase checks for speaker configuration up to 10.2. It calculates flexible and highly accurate signals that are saved in AIFF and WAV (BWF) sound files up to 192 kHz. In addition, it leaves markers in the sound files indicating the exact frequency or amplitude at that location.
Why do I need to create a test tone?
There are a number of situations where test tones are useful, from standard reference tones that precede recordings (with Make a Test Tone, you can choose to input test tone specifications with the spoken word), to measuring and adjusting room acoustics. In general, test tones can help detect deficiencies in acoustic situations, recording, signal processing, and wiring.
Why did Audio Ease create this application?
Audio Ease has used the signal generation algorithms in Create a Test Tone extensively in producing signal processing algorithms. For example, we use these tones for quality checks of the sample rate conversion, word length reduction, and early compression algorithms in BarbaBatch (our batch sound file conversion package). Tones have proven to be a very valuable addition to listening tests with musical and speech fragments.
How to use Create a test tone
First, you select one of the following algorithms by clicking on the first three tabs:
- Single Test Tone
- Full Bandwidth Scan
- Scan custom
With the third option, you can create the tones and sweeps of the first two and more, but you will need to pass more parameters.
Then you give the chosen algorithm some parameters which describe the exact test tone you want, using radio buttons and editable text boxes.
indicates whether you want the testtone to be entered with spoken text (a female voice says, for example, " thousand Hertz minus ten points zero decibels zero, sampling rate 44.1 kHz"
When you do, press the 'Generate sound file' button in the lower right corner: a dialog ' Save' will be displayed one way.
You choose a name for your sound file or leave the one suggested by Make A TestTone intact, navigate to a folder where you want to save the sound file and choose one of the sound file formats available: AIFF, WAV (BWF). Then you click 'Save'.
When the processing time exceeds one second, a progress bar will be displayed.
0.5ms linear fading is applied to avoid one click at the end of the file. Since the initial phase of the generated sine is always 0, a fading is not necessary. We will now go through the three algorithms, their parameters and their applications, one by one.
Simple Test Tone
For this tone, you need choose a frequency, a level, a duration and a sample. The tone will be invariant in amplitude and frequency. For the sampler, you must choose the material rate of your digital program. A marker is dropped at the beginning and end of the resulting sound file, listing the sound parameters. You can only see these bookmarks when the sound file is opened in editing software that recognizes bookmarks. A default application for these tones is the reference tone that is often required before recording material on tape or disc. Classic values for this tone are 700 Hz, 1000 Hz and 10000 Hz, all at -10 dB and lasting 10 seconds each. These values are standard frequencies for adjusting EQ, polarization, levels, tape speed and azimuth on analog recorders, but are still frequently used in the digital domain. If you put one or more reference tones before a recording, make a 20-second silence between the sound and program material. This will allow for future background noise fading and, most importantly, this is a safe margin for any copying effects that might occur due to the tape layers curling over each other. Completely document the reference tones of your choice.
Full Bandwidth Sweep
With this method, you create a frequency sweep exponential ranging from 5 Hz to half the sample of your choice. (On a 96 kHz sample, the tone ranges from 5 to 48000 Hz.) You can provide a (constant) level. Scanning is exponential. This means that it increases with a fixed number of octaves (or 'interval'), not with a fixed number of Hz per second. Approximately two markers are discarded every second, containing the exact frequency at that point. If you want to know where the bookmarks were dropped and why, read the 'About bookmarks' section. As all frequencies from 5 Hz to over 20 kHz are covered, scans produced in this way can be used to check the shape of a filter's frequency response (almost all elements in a signal path can be considered filters, see 'About Frequency Response').
Observing the filter curve of a software equalizer
Create a full bandwidth sweep on a 44.1kHz sample, at -12dB, 10 seconds
load it into your editing system and apply the equalizer of your choice
The resulting sweep envelope, or waveform overview shape, is actually the frequency response or filter curve you want to examine. If you have software that recognizes the markers dropped in the scan file by Make A TestTone, the x-axis of the screen can be used as a frequency ruler.
Checking the quality of a sample rate converter .
If you need to decide on a sample rate converter to use on critical materials, take a closer look at its quality. Let's take a typical case of CD premastering.
Create a full bandwidth sweep on a 48 kHz sample at a level of -3 dB, 20 seconds long.
Use a sampler converter to convert it to 44.1 kHz.
Make sure the clock on the playback machine is set at 44.1 kHz before reproducing the result. (In SoundDesigner, for example, this is done using the Hardware Setup dialog.)
touch scan back.
Run this test with all available sample converters and choose the best. (Don't forget to download the latest version of BarbaBatch from the web, to include both sample converters in the test...) If you want to run the test with different samples, you can use the 'Custom Sweep' method.
Other tests
In the examples above, we stay in the digital domain, as it is much less complicated than performing similar tests in the analog domain. It is not enough to just listen to a scan played back in a room if you want to draw sonic conclusions about the acoustic characteristics of that room. You will measure many things at once: playback system -> amplification -> speakers -> living room -> ear. The peaks and dips you notice could be on any of these filters in the chain. In general, you want to isolate an element in the chain to find its characteristics. This can be done, for example, by knowing the frequency responses of all other elements and taking them into account when looking at the results. Some professional equipment comes with a frequency response measurement chart, allowing you to do just that. In laboratory situations, anechoic rooms are used for the same reasons: excluding, in this case, the room itself from the complete chain of measurements. Using an accurate level meter (on your mixing console) at various stages of the chain can also help. While playing back the sweep, the meters follow the frequency response of the element you are measuring. Try your own room with a full bandwidth scan to see how flat the entire string is. You will often hear very distinct peaks and dips. If you want to 'zoom in' on the suspicious area, use the 'Custom Scan' method to restrict the frequency parameters while maintaining the length. Recording the scans back to the hard disk recorder allows you to view the envelopes (the frequency response) of the results. the fourth in the complete chain of measures itself. Using an accurate level meter (on your mixing console) at various stages of the chain can also help. While playing back the sweep, the meters follow the frequency response of the element you are measuring. Try your own room with a full bandwidth scan to see how flat the entire string is. You will often hear very distinct peaks and dips. If you want to 'zoom in' on the suspicious area, use the 'Custom Scan' method to restrict the frequency parameters while maintaining the length. Recording the scans back to the hard disk recorder allows you to view the envelopes (the frequency response) of the results. the fourth in the complete chain of measures itself. Using an accurate level meter (on your mixing console) at various stages of the chain can also help. While playing back the sweep, the meters follow the frequency response of the element you are measuring. Try your own room with a full bandwidth scan to see how flat the entire string is. You will often hear very distinct peaks and dips. If you want to 'zoom in' on the suspicious area, use the 'Custom Scan' method to restrict the frequency parameters while maintaining the length. Recording the scans back to the hard disk recorder allows you to view the envelopes (the frequency response) of the results. the meters follow the frequency response of the element you are measuring. Try your own room with a full bandwidth scan to see how flat the entire string is. You will often hear very distinct peaks and dips. If you want to 'zoom in' on the suspicious area, use the 'Custom Scan' method to restrict the frequency parameters while maintaining the length. Recording the scans back to the hard disk recorder allows you to view the envelopes (the frequency response) of the results. the meters follow the frequency response of the element you are measuring. Try your own room with a full bandwidth scan to see how flat the entire string is. You will often hear very distinct peaks and dips. If you want to 'zoom in' on the suspicious area, use the 'Custom Scan' method to restrict the frequency parameters while maintaining the length. Recording the scans back to the hard disk recorder allows you to view the envelopes (the frequency response) of the results.
