Computer Music (MUSC 216)
Blair School of Music
SYD Tutorial 10
Deconstructing Natural Sounds
Deconstructing a natural sound involves analyzing the spectrum of the sound in order to recreate it using the various techniques of sound synthesis (additive, FM, subtractive, wave shaping, etc.). The sound you will create in this tutorial is the sound of a flute-like instrument called a RECORDER. Click below to hear a note played on a recorder:
After analyzing the spectrum of this sound and using that information to reconstruct it using additive synthesis techniques, you will create this sound:
[Although SYD is available in versions for both Macintosh and IBM computers, Amadeus II is only available for Macintosh. There may be other spectrum analysis tools available for IBM computers but this writer is only familiar with MAC OS applications. GOOD LUCK!!]
This tutorial will be divided into the following sections:
Begin by downloading the recorder sound file:
Launch the application, Amadeus II.
From Amadeus II, open the sound file you just saved, RecorderSound.aiff
You should see the following:
Figure 1: Recorder Sound File as viewed from Amadeus II
Select a region of the sound file for which you will examine the frequency spectrum:
Figure 2: Recorder Sound File with region selected as viewed from Amadeus II
From the 'Analyze' pull-down menu in Amadeus II, select 'Spectrum':
Figure 3: Select 'Spectrum' in the Analyze pull-down menu in Amadeus II
Click 'OK' when you get the Spectrum Options window:
You should see this graphic which is a representation of the individual frequencies (harmonics) of the note, A4 played on a recorder.
Figure 4: Sound spectrum of the note A4 played on a recorder as viewed from Amadeus II
Place the corsair (corsairs) exactly over the leftmost frequency in the spectrum:
Figure 5: Frequency and Decibel (dB) levels of the note A4 played on a recorder as viewed from Amadeus II
In a convenient location, write down the values of the frequency and decibel (dB) levels. Repeat this for each of the other two frequencies in the recorder spectrum. You should end up with these approximate values:
The next step is to convert the decibel (dB) levels to real amplitude values on a 100% scale. You will be synthesizing the recorder sound using SYD. SYD uses amplitude values on a 100% scale and does not use decibel levels. The relative loudness of sound is usually referred to as the 'sound intensity level' and is based on the threshold of hearing at 1000 Hz. [For detailed information, check out SOUND INTENSITY LEVEL.]
Here is the formula:
After converting each decibel level, you should get the following amplitude values:
CREATING THE BASIC SYD PATCH
Create the following patch with a output duration of 4.0 seconds:
Figure 6: Basic Recorder Patch using SY
You could put an envelope on each of the three oscillators. But, because one of the amplitudes from the decibel (dB) to amplitude conversion table [Table 2. above] is > 1.0, it is best to patch the outputs from the oscillators through the mixer. This attenuates the amplitudes proportionally such that the overall amplitude coming out of the mixer is <= 1.0. Consequently, it is more convenient to put the envelope on the amplifier.
The recorder is a 'woodwind' instrument (wind instrument) which requires wind pressure from the breath to produce the sound. The basic woodwind envelope [which would also include such instruments as flute, clarinet, oboe, bassoon, or any reed instrument which requires the human breath to produce the sound] looks like this:
Here are the specific parameter settings for the woodwind envelope for the above patch:
When you synthesize the patch, it should sound like this:
ADDING BREATH NOISE TO THE BASIC SYD PATCH
Adding breath noise to the basic recorder patch involves using the Butterworth filter set to BANDPASS mode. You will add three bands of noise roughly matching the three frequencies derived from the spectrum analysis above.
Here is the next stage of the Recorder Patch:
Figure 9: Basic Recorder Patch with Noise added using Butterworth Filters using SYD
Look for the three Butterwoth filters which have their output to a mixer and then to an amplifier, just like the Basic Recorder patch described above. In addition, the same envelope controls the amplifier for these additions.
In order to more easily control the noise level, an FTAB function has been incorporated. Here are the parameter settings for the FTAB:
Figure 10: Parameter settings for the FTAB function using SYD
The 'Function' field will contain the basic BANDWIDTH for each filter. Here is the format for using the FTAB function in the BUTTERWORTH filter:
Figure11: Parameter settings for the Butterwoth Filter using SYD
Note the format of the the FTAB function. The values in the parentheses (0,1) refer to the FTAB number and the value in the FTAB 'Function' field respectively. See the SYD User Manual for more detailed information on the use of FTAB. Each BUTTERWORTH Filter will have similar settings where the value in the 'Freq' field corresponds to the value of the corresponding frequency from the spectrum analysis above. The value which is multiplied with the FTAB function, is the amplitude for the corresponding frequency. Here is a table which shows these values:
When you synthesize the patch, it should sound like this:
Compare with the Basic Recorder Patch:
To increase or decrease the amount of noise you would like in your Recorder sound, change the value in the 'Function' field of the FTAB operator. A higher value (eg., 300) will give you a lot more noise; a lower value (eg., 100) will give you less noise.
ADDING THE FINAL SOUND CHARACTERISTICS TO THE BASIC SYD PATCH
[Sorry, not done yet.]
Try analyzing and then synthesizing the following musical instruments: