Noise emission: The sound pressure level in dBA
Measuring the noise level is a bit tricky, but works quite well in the evening hours at the measurement location. We chose dBA and deliberately decided against sone because values below one sone can hardly be reliably measured with still affordable and calibrated equipment. Sone is also a rated specification and the software conversion of various software programs in this low range is rather confusing and inaccurate. Then rather dBA, especially since most people can do something with it and you can also check the manufacturer’s specifications. The measuring distance is 50 cm from the center axis of the fan inlet.
The graph is also new because it includes the measurement on the radiators. This makes it easy to detect various resonances and to recognize speed-related humming from the curve. The slider is again at the start and the colors of the curves are uniform.
What is also new are the long-term measurements on the radiators, which we offer you as MP3 files. A total of 4 files can be compared well with each other this way:
Case fan
25 mm radiator
45 mm radiator
60 mm radiator
We take two approaches to these measurements. For quick and plausibility tests, we use a Voltcraft SL 451, which we have calibrated according to ISO and whose microphone we have placed decoupled from the body. The data acquisition takes place outside the measuring chamber. It is also the only component that has not been acquired by ourselves. All other measuring instruments including accessories and electronics were purchased by us or provided from private stocks. However, no really resilient levels can be measured with it and we only use it for preliminary tests and quick checks.
Our own acquisitions therefore include a calibrated measurement microphone with XLR connector and low-noise USB interface. The measurements are taken in the evening and night hours in a rural area in a large, insulated basement room, so that one can already be quite satisfied with a basic level of well below 26 dB(A). Since everything will be above this anyway during the measurement setup with a distance of 50 cm, this should therefore not be a problem.
We also took the feedback from the community and for certain speed ranges we also evaluated the frequency band in detail, so you not only get the SPL values (sound pressure) in dB(A), but also a nice frequency analysis that helps to describe the sound character perfectly. Bearing or motor noises, vibrations or the tearing noise on the rotor – everything becomes mercilessly visible with it.
We won’t go into certain details and solutions in this article, because there is still some foreign know-how in this setup and some things would probably be too far for the normal consumer.
Whoever is interested in this and would like to build something like this, is of course welcome to contact us. This also applies to all those who would still like to contribute suggestions and tips, because in the meantime we are no longer at the very beginning, but there is certainly still something to correct or expand.
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