deciBel is the result of a serious effort to make an Android based SPL meter as close to a professional-grade device as the phone hardware limitations allow. It uses a Fast Fourier Transform algorithm to implement high precision A, B, C and Z weighting filters and sophisticated digital signal processing techniques to achieve the best possible SPL readings out of your Android phone or tablet. It displays the current, maximum and minimum values in decibels, and generates 3 kinds of sound pressure level versus time charts. The display can be turned upside down to allow pointing the mic at the sound source. Please calibrate before the first use! Features:
 Fast Mode This is the default screen. It displays the current, maximum and minimum sound pressure levels in decibels and a moving dB x time chart. The display and the chart are updated every second and the chart data slides continuously to the right to always show the last 5 minutes of the recording.  Slow Mode In this mode the chart is updated once each 15 seconds and you can resize the time axis to 15, 30, 60 or 120 minutes. The chart shows three lines: The 15 second average in orange, the minimum (in each 15 seconds) in yellow and the maximum in red. Once the chart data covers the whole selected time span, it begins to slide to the right.  Accumulated Exposition Time This mode is a histogram that shows how many time the device was exposed to each sound pressure level since the beginning of the measurement. The time axis starts in seconds and evolves to minutes and then hours. The sound pressure levels are 5dB wide. It resembles the functionality of a sound level dosimeter.  Main Menu The phone menu button brings up the deciBel main menu with options to show the Help or About screens, to rotate the display, to call the calibration tool and to quit the application.  Rotated Display Selecting the Rotate Display option in the main menu causes the entire display to rotate 180 degrees. This can be very handy if you want to point the mic, which is located at the bottom of the phone, to the sound source.  Chart Menu If you touch the chart image for 2 seconds this context menu will show up. Select one of the options to change the chart type or to save a chart screenshot to the sdcard. Unlike the phone menu button, which can emit a click, the context menu is silent and does not disturb the running measurement.  Display Menu If you touch the numeric display for 2 seconds this context menu will show up. Here you can select the weighting curve and reset the saved data: Select the Reset All option to reset the displayed Max and Min values and to restart the logging charts. Or select the Reset Max and Min option to reset these values only.  Calibration Panel Use this screen to trim the deciBel sound pressure meter to your particular hardware to achieve more precise measurements. Even high end sound pressure level meters must be calibrated from time to time due to inevitable changes in hardware characteristics. For calibration instructions, please see the Help page. There are two flavours of deciBel: 
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