User's Manual - Cornell Lab of Ornithology - Cornell University

Chapter 4: Amplitude CalibrationSelectingcalibrationparametersPressureSelect two calibration parameters by clicking two radio buttons next to theterms Pressure, Intensity and Characteristic Impedance. The values shown forthe two parameters that you select can be edited. The value of the thirdparameter is calculated by Canary from the other two, according to Equation4.1 or 4.2.The pop-up menu next to the value shown for Pressure indicates whetherpressure is expressed in absolute pressure units (pascals, abbreviated Pa) or indecibels (dB). If you choose dB, the value in the Pressure field is taken as dBrelative to the pressure reference value specified in the Pressure dB re field inthe lower left part of the dialog box (see below). You should select the unitsbefore entering a value into the Pressure field.A second pop-up menu lets you specify whether the value in the Pressurefield will be the RMS, Peak, or Ceiling value for pressure. Figure 4.2 illustratesthe relationship between Ceiling, Peak, and RMS values. If you choose RMS,the value is taken as the RMS pressure value of the entire signal. If you choosePeak, the value is the pressure value of the individual sample with the largestabsolute value. If you choose Ceiling, the value is the pressure represented bya sample in which all bits are equal to 1. 1 You should select RMS, Peak orCeiling before entering a value into the Pressure field.peak = 1.58 Paceiling = 2.0 PaRMS = 0.78 PaFigure 4.2. Relationship between ceiling, peak, and RMS values of a signal.Canary lets you assign an absolute amplitude value to any of these threevalues. This signal has been calibrated to set the ceiling equal to 2.0 Pa (=100dB re 20 µPa).If you selected Pressure as one of the two parameters to be set (by clicking oneither of its radio buttons), enter the RMS, peak, or ceiling pressure of theentire signal. If you are using a pure-tone calibration signal of knownamplitude, as discussed above, you will probably want to specify the RMS orpeak pressure.If you did not select Pressure as one of the two values to be set, the pressureshown will be the pressure that Canary has calculated from the current valuesfor Intensity and Impedance.1 The ceiling value thus corresponds to 128 for 8-bit samples, or 32768 for 16-bitsamples.Canary 1.2 User’s Manual 73