OboeTester channel frequencies are too high for ChannelMask 7.1.4

[philburk]

Android version(s): all
Android device(s): all
Oboe version: 1.9.1
App name used for testing: OboeTester

Short description
Sine wave are too high pitched for humans. Fine for dolphins.

Steps to reproduce
Run TEST OUTPUT
Select ChannelMask: 7.1.4
Turn down Volume slider (just below channel checkboxes) all the way.
Press OPEN then START
Turn off all the Channel checkboxes.
Turn up the volume slider.
Turn on each channel checkbox one-by-one.

Expected behavior
Be able to easily hear each channel.

Actual behavior
The higher channels are very high pitched and unpleasant.