Quick Start Guide

Last Update: 1/4/21

Applications Manual for Sound Recording with iOS

9. Testing Methods

Sonic Presence’s Level Test Setup and Measurement Procedure

In order to accurately measure signal levels and determine the precision of meter readings you must use calibrated test

signals. For our acoustic tests we used an ANSI S1.40 - 1984 calibrated sound generator. It produces a 1kHz sine wave

signal, which is switchable between 114dB and 94dB SPL (Sound Pressure Level). The International standard for testing

microphones is 94dB, which is equal to a pressure of 1 Pascal. When we do our final testing of the Sonic Presence Spatial

Microphones, we set the output level to equal 0dB Full Scale at 124 dB SPL. That is as loud as it gets at a heavily amplified

Rock Concert. This choice of signal level guarantees there will be no distortion caused by the microphone. If there is

distortion in your recording, it’s because the Input Gain is set Incorrectly.

We made our test measurements by inserting the Sonic Presence sensors directly into the sound generator’s calibrated

sound chamber. For our digital measurements, we used a 1kHz function generator with an output signal amplitude that

we could adjust in steps of 0.1 millivolt. We then injected that signal into the analog sensor input of the Sonic USB

Interface. (CAUTION: You should not try this at home. You could permanently damage the unit.)

For both of these measurements, the Sonic Presence’s digital output signal is then plugged into the USB port of the test

device to determine the digital signal levels. We used three different measurement Apps to insure the accuracy of our

digital test signal. The first is the ProLevel Meter App from Katasura Shareware. The second is Apple’s Logic Pro X App and

the third App is MusicScope from XiVero. All of these Apps are running on a MacBook Pro computer under OSX.

Function

Generator

Sonic Presence

USB Interface

analog

digital

Acoustic

Generator

sensor