Posted by: recordingsofnature | May 21, 2015

Field recording 5 am Valby parken, May 12th 2015

This is a nature recording at 5 am in Valby parken, May 12th 2015. This spot is a relatively desolated area located near the water and just 6 km south of Copenhagen centre.
The morning was a calm, moderately warm and moist with wet grass. At 5 it was just getting light, and birds were very active. During the recording you can also hear the motorway across the water and the city waking up slowly. Recording setup 5 o'clock

 

Panorama view of the recording site

Panorama view of the recording site (composed with Hugin free software)

View towards the motoway at Avedøre Holme (also stitched with Hugin)

View towards the motoway at Avedøre Holme (also stitched by Hugin)

 

Setup
For this recording I’ve used a new binaural setup which features the QTC40 microphones together with the artificial ears as described the last posts.
The binarual recording head with qtc40 microphonesI think this configuration produces the typical binaural characteristics, including very high channel separation of the two ears pointing completely opposite direction. This gives a wide stereo image but with lesser definition in the direct forward direction. It is a different listening experience compared to more classical and semi binarual methods. I think each methods have their strengths.

I’m using a simple noise-test to test and characterize the microphone setup. It is a way to get a quick impression of the sound, directionality of the stereo image and frequency response. The test consists of making a noise sound (e.g. by rubbing two crisp, thin plastic bags) with 45 degrees intervals around the setup, distance 1 meter. The noise spectra for different directions can then be compared and normalized to the spectra of clean microphones to see the gains of the setup.

Here is the noise test performed in the field for the present recording (after EQ):

Below is the results from a more throughout test of the binarual setup performed in my living room.

Binaural head frequency response, indoor

Thick black line is the average response from all directions. Thin lines are all the individual directions. Thick magenta is average noise spectrum from clean microphones.

I have attempted to equalize the present recording according the average directional response to get an overall neutral response. These are the EQ settings used:

eq1

 

The spectrum has a valley around 3.5 kHz, which is a result from a reflection of the ear canal and the cotton wool “tympanic membrane”. Without the ear canal the response would be one large peak ranging from 2-7 kHz. By adjusting the length and dampening of the ear canal it is possible to acoustically tune the ear response.

Close-up of binaural ear without wind shield

The QTC40 microphone enters from the back side with the tip just at the ear canal entrance. Inside the ear canal is a piece of cotton wool to dampen the resonances.

At the moment I dont know what the optimal settings are, however, with the current configuration I have tried to let it match the response obtained when measuring on my own ears

 

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Responses

  1. […] The recording starts with me walking the last meters and placing the recording gear near the water. In the beginning, at 3 am, the only singing bird is a distant nightingale, but shortly with the first light, the colony of black headed gulls wakes up. Steadily, the sound level builds up with greylag goose, lapwing, cuckoo, redstart, wren, black bird, joining in. (Im still missing the balck cap, which was very active at this time last year) […]

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