Realization of Microphone Volume Intensity Indication Ondrej Krejcar 1,2 and Dalibor Janckulik 1 1 Department of Measurement and Control, Faculty of Electrical Engineering and Computer Science, VSB Technical University of Ostrava, Ostrava-Poruba, Czech Republic, ondrej.krejcar@remoteworld.net, dalibor.janckulik@hotmail.com 2 Department of Information Technologies, Faculty of Informatics and Management, University of Hradec Kralove, Hradec Kralove, Czech Republic, ondrej.krejcar@asjournal.eu Abstract. In many desktop applications, an audio signal is captured from the microphone. Unfortunately, most applications lack quality visual indication of arousal microphone volume, which would clearly provide to users (surveillance) information on current values and, if so achieved within a short past. The usability of applications could be in using it as an acoustic monitoring or as a visual area, or volume level for the detection of a communication program. Usability is, of course, also in programs for recording and monitoring audio. The component is designed in .NET Framework. Keywords: sound level meter, VU meter, sound, sound card, microphone 1. Introduction To zoom the project physical foundation of a problem can be applied. In words of basic physics definition of sound, the sound wave is a periodic compression and expansion of flexible space in which it spreads, for example, air, water. The sound is perceived by a hearing body volume. Loudness is a subjective variable and depends on the sensitivity of hearing. For an objective evaluation of sound there was introduced so-called sound intensity I which is defined as the proportion of sound power P waves and area S through which the wave passes. According to the sensitivity of a human ear there are established two boundaries of sound intensity:  threshold of hearing - it is the smallest registerable audio enjoyment - 20μPa (sound).  threshold of pain - it's a border where the man begins to feel the pain and the sound can cause permanent damage - 130Pa (sound). To better distinguish the volume levels of sound there are used logarithmic coordinates in units of dB, because the human ear can detect the order of just 1 db [1]. To record or work up an audio microphone, which converts sound into an electrical signal, is used. Since each microphone is not able to process signals from a full spectrum, the different types of construction working at the other physical laws, according to the required properties. The most widely used electrostatic microphones are microphones that have a high output impedance, balanced frequency response, high sensitivity, low distortion and high stability of their properties. With the audio card they are connected to the computer. Because of the analogue input signal A / D converters are used in sound card [2]. The transfer takes place by the means of sampling. This means that at each time interval the current status of the signal is detected and recorded (sample). It is obvious that the shorter this interval is, the higher the sampling rate is, the more samples will be acquired and the resulting record will be better [3]. As a similar interpretation of this project let's include the so-called VU meter or PEAK meter, thus measuring devices showing the actual value (intensity) of audio signal. In former times it was formed by an analogue magneto device with calibrated scale, currently LED-vertical or horizontal scale (bars) are used more [4]. 2011 International Conference on Software and Computer Applications IPCSIT vol.9 (2011) © (2011) IACSIT Press, Singapore 127