This options screen presents options for input and output devices. Some options, like calibration, are not available for the built-in accelerometer. Device calibration is also unavailable when working with units of FS for the selected audio device.
- Input Device
Tap Input Device to select between the current audio input, as determined by iOS, and the built-in accelerometer.
- Input Channels (Follow this link to learn more about input channel options.)
- Device Units
Use the Device Units segment control to select the desired units for the input device.
Tap Calibrate to manually enter a sensitivity for the input device, or automatically calibrate its sensitivity based on a known input level.
- E.A.R.S. or UMIK-1 Reload Factory Calibration Data
When a miniDSP USB microphone, such as the UMIK-1 or EARS system, is connected, an option is available for reloading the factory calibration information by entering the microphone's serial number (an internet connection is required to download the factory data). Overall sensitivity and frequency response data will be loaded. User calibration may still be performed for either of the UMIK-1 or EARS system's two input channels. Frequency response correction and overall sensitivity may be applied independently to each channel, even if the same signal is present on both channels, as it is with the UMIK-1.
Some input devices support software control over the hardware input gain. When the device supports it, an input gain slider and text box are available, both to see the current input gain and to make adjustments to it. With the miniDSP USB mics, the gain can be adjusted from -31 dB to +24 dB in 1 dB increments without the need to re-calibrate.
- Audio Play Through
Turning this switch on will cause the audio input signal(s) to be routed to the current output device. It may be best to turn this option off when working with the built-in signal generator.
- Prefer Speaker Output
On the iPhone, the default audio output device is the receiver. The receiver is the small speaker embedded in the front of the device, above the screen (it is used by the Phone app). Switching this option on will cause the built-in speaker to be used for audio output, regardless of what other audio connectors or accessories are attached to the device.
- Desired Sample Rate
In this text box, you can enter the sample rate (in Hz) that you would like the hardware to operate at. If that sample rate is supported, it will be selected by iOS. Otherwise, the closest supported sample rate will be selected. The built-in mic and headset input can typically operate at sample rates between 8 kHz and 48 kHz (e.g. 8k, 11025, 12k, 16k, 22050, 24k, 32k, 44.1k, 48k). External audio devices can sometimes operate at higher sample rates (even up to 192kHz for USB audio interfaces).
- Actual Sample Rate
This displays the sample rate at which the audio hardware is currently operating. The Octave Analyzer tool only supports sample rates of 44.1 kHz and 48 kHz.
- Measurement Mode
Measurement Mode disables the auto gain control and high-pass filter that are otherwise applied to the built-in mic and headset inputs.
- Audio Session Details
Tapping on Audio Session Details will present a detailed description of the current audio input and output paths.