ark said:
domivr said:
Do you have some units for the vertical axis on the second picture?
The audio program that I was using as a quick fix does not give any units. To get units I will have to use more specialized power spectrum analyzer. It will take a couple of days until I have time to do it.
Don't worry about it ark. I was trying to make sense of the energy in the peaks at around 700Hz and 1kHz. Knowing the scale/units (e.g. dB scale) would make it easier. Right now I am hypothesizing it is the "wind like" noise.
Regarding the bees hypothesis, I dug up some info from two papers:
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1. "Schwirrläuferinnen" buzz their wings every 0.5 to 3 sec while performing straight runs. The frequency within a buzz varies between 180 and 250 cps.
2. The "Schwirrläuferin" produces a permanent noise as soon as it contacts a hivemate. In this permanent noise the frequency increases to about 500 cps.
3. In the permanent noise a second, constant and independent sound with a frequency of about 5,000 cps shows up. Its amplitude can reach 1/3 of the amplitude of the lower frequency noise.
4. Bees in a non-swarming hive react to tape recording of contacting "Schwirrläuferinnen" with the "freezing" response. This response can not be elicited in swarming hives.
buzz runners = Schwirrläuferinnen
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The sounds of honey bees and social wasps are always composed of a uniform frequency
Jacob S. Ishay
Department of Physiology and Pharmacology, Sackler School of Medicine, Tel-Aviv University, Ramat-Aviv 69978, Israel
Dror Sadeh
Department of Physics and Astronomy, Tel-Aviv University, Ramat-Aviv 69978, Israel
The sounds produced by the honeybee Apis mellifera (Apidae) and by the social wasps Par avespula germanica and Vespa orientalis (Hymenoptera, Vespinae) are of a uniform frequency which nevertheless differs in accordance with its purpose. In honey bees, the sound produced by ventilating workers has a frequency of 309 Hz, whereas that produced by the queen (queen piping) has a frequency of 450 Hz. In P. germanic a, the sound frequency during ventilation is 194–231 Hz, whereas in V. orientalis, the ventilation and the awakening dance sounds (produced by the workers) and the hunger signal (sounded by the larvae) have a frequency of 118–140 Hz, while the threatening flight occurs at 221 Hz and the dance of workers facing the queen—at 600–637 Hz. All the produced sounds are synchronized to a uniform frequency over a given period, regardless of whether they are produced by a single insect or by an entire group. However, the frequency may change with time, probably owing to fatigue of the producer, and also the intensity of the sound may change, which results in a great variability of the sounds despite their uniform frequency.
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The 500Hz peak is consistent of evidence of bees (based on 1st piece) but there is no peak at 5kHz in the spectrum analysis. Maybe this is a recording device bandwidth issue.
