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Assigment-4: Flutes and Warnings

September 11, 2009

The two recordings I used for this project were the sound of a sustained flute note and the sound of a woman saying ” We will not be held responsible for any hearing imparments or damage caused by excessive exposure to this sound“. Below are the images of the sonic visualizer analysis of the two sounds:

The flute note shows a very predictable pattern of loudness that grows, establishes a certain decibel level, then drops off with some variations that result in the flow of air being truncated. One interesting variation however is the spike and then drop in loudness at the beginning of the sound that could result from an attempt to establish a vibrato in the note too early and result in a reduced air flow.

The pitch of the flute note also remains extremely constant. The player seems to be very proficient with this instrument as the vibrato shifts between two steady pitches at a regular rate. There is also no significant slide of the pitch into the desired note. At the end of the sound, the pitch rate spikes, possibly from residual harmonics in the tube section of the instrument that continue to resonate at high frequencies after the air flow has stopped. Since the jump in pitch coincides on the time scale with a drop in loudness, I assume this is the case.

The brightness of the flute shows interesting characteristics that I find indicative of the instrument mechanics. When the note is started, the initial airflow into the instrument released with the greatest pressure, causing the frequencies making up the pitch to have more energy and produce a brighter tone. The brightness settles into a steady rate with slight variations. At the end of the note, the air in the flute trails off, leaving most of the residual harmonics with a less bright tamber before the instrument is silent.

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In the speech sample there seemed to be a relationship between the loudness and the pitch. Higher pitches tended occur in quieter segments, although there was plenty of variation in the sample to preclude making a causational hypothesis.

Higher pitches seemed to be correlated with vowel sounds rather than consonant sounds which made detecting which parts of the recording matched the graph very difficult since most words begin with consonants and that is where our speech patterns tend to focus stresses. The variation in pitch within a fairly low range seems typical of speech. It would be interesting to compare the pitch and brightness of this sample with a similar phrase spoken by a man or by a person with a different accent.

The brightness of the sounds were also highly variable but unlike the pitch, were in a much wider range of frequencies. This is not surprising considering the variability with which people form words by manipulating airflow in the mouth. I think that when a flute plays and the airflow is stopped, the brightness goes down because there is no more variation in the sound. But when humans stop talking and the airflow dies, it is still being manipulated in a myriad of ways that change the shape of the resonances and therefore the brightness.

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One Comment leave one →
  1. September 13, 2009 6:29 pm

    Amazing the description of the flute sound, 10!!!!

    In speech the consonants are noisy sounds that do not have a pitch, thus we have to be careful when we interpret the pitch curves in speech. What we see in the parts of the consonants is an error of the detection algorithm.

    Also the measure of brightness, spectral centroid, during quiet parts of speech should not be considered, we are basically measuring the brightness of background noise, which is very bright, but so quiet that it does not matter.

    …xavier

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