We are developing a new evaluation of acoustics properties of wood and wood panels with small dimensions and in the free-free scheme for vibration testing is necessary a microphone to pick up the signal.
Ricardo, acredito que possa ser empregado um microfone convencional. De uma olhada no artigo desse link: https://periodicos.ufpel.edu.br/ojs2/index.php/cienciadamadeira/article/view/4066/3210
Ricardo, assuming you have estimated via theoretical calculation or simulation the sound pressure level you expect to be produced from your acoustic structure/system, you would then select a measurement microphone that has the required sensitivity (in milli-volts/Pascal, for example) and noise floor (noise equivalent pressure, S/N ratio) to give you acceptable results. For a quick example, if your calculations tell you that you expect an rms sound pressure level of 65dBSPL, and you need at least 20dB of S/N ratio, then you select a microphone that has at least a noise equivalent pressure of 45dBSPL...however this is a very brief and simplified explanation. The details of the measurement set up (distance of microphone from the source), and the bandwidth required, if it is in a free field environment (no acoustic reflections) or reverberant environment are all important factors to know about in order to answer the question more accurately...Check out Bruel & Kjaer or DPA for high quality acoustic measurement mics...we typically used these at Bose Corporation...hope this helps
I would suggest measurements with a laser vibrometer! If available...
Vibration sensors and also Microphones are provided with varied specifications, but simply there are three main features which can help you to chose your proper sensor:
1- sensor response bandwidth (frequency response bandwdith): it depends on the phenomenon you are going to survey, a sensor with a more broader bandwidth is more expensive
2- sensitivity: in volts/g, or pc/g, or volt/pascal, ...
the price goes up with sensitivity, depends on the lowest level of the measured signal and the minimum resolution of the analog/digital convertor, and also the signal to noise ratio of the measured signal you need to chose a minimum sensitivity
3- dynamic Range of the sensor : which is the ratio of the maximum measurable level to the noise floor of the sensor,
sensors with greater dynamic range are more reliable and more expensive.
the maximum measurable limit of the sensor is important because it could clip when triggered with the higher level of input
The microphone should be placed in a well defined position according to "Standard Test Method for Dynamic Young’s Modulus, Shear Modulus, and Poisson’s Ratio by Impulse Excitation of Vibration", so microphone membrane should not be big if you want to pick signal from that point.
Thank you all for the answers! I learned a lot with them and I will try some advices that you told here.
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