Manual in PDF format:
http://withstrings.com/withstrings_audioanalyzer_manual.pdf

1. Description
Audio Analyzer acquires a signal from the device's microphone and displays its
time-history and Fourier amplitude frequency spectrum (using a FFT algorithm).
Sampling of the time history starts when the amplitude of the audio acquired at
the microphone is greater than the adjustable trigger level slider. The length of
acquisition is adjustable from 0.05 seconds to 1 second. Vertical scales for each
of the graphs are independently adjustable or can be set to auto-scale. A cursor
for each graph has three settings: off find peak or find value using a slider.
Linear or logarithmic amplitude displays are available for the vertical axis of
the frequency graph. Data from the graphs are 4096 points and can be saved to a
spreadsheet compatible formatted file.

2. Operation
Launch the application. Audio Analyzer will display a screen similar to figure 1.
The cursors are initially off frequency range is set to 20Khz and vertical
scales are set to Auto mode. Pressing the Run button will start acquisition if the
input amplitude is greater than the trigger level. Adjust the Trigger level for
the desired sensitivity by moving the red circle on the trigger slider.
The Freq(Time) button produces inverse results on the time and frequency graph. A
wide frequency setting of 20Khz will produce a very small time sampling window of
0.05 seconds. Conversely a 1Khz frequency range will produce a sampling window of
1 second.

A cursor is available for each graph. Pressing the cursor button one time will set
it to peak mode. The peak (positive) will be shown on the graph with cross-hairs
on the graph; its xy coordinates are displayed in blue font on the upper right
side of the graph. Pressing the cursor button again will allow the cursor cross-
hairs to be dragged to any data point on the graph. The xy coordinates of this
point are displayed in blue font on the upper right side of the display.
Vertical scales are adjustable for each graph. Auto mode will find the best scale
to display all of the datum on the graph. Pressing the scale button will set the
vertical scale to one of several predefined scales. Clear will erase data and
clear both time and frequency graphs.

The Lin/Log button when set to log mode shows the vertical scale equaling the log
of the value. This is ideal to find small frequency peaks that are otherwise
buried in the spectrum display.

The Save/Send button will capture the time and frequency graph to a comma
separated variable file in the following directory:
.../Android/data/com.withstrings.audioanalyzer/files. Note all data in this
directory will be erased if the app is un-installed. The data file has the format
shown in figure 2. When the save button is pressed a dialog will appear where the
file just produced can be sent elsewhere by one of the email apps on the device.
There are four columns in the exported chart shown in figure 2. The first two are
from the time graph showing time and audio amplitude. The next two columns are
frequency and amplitude from the Fourier amplitude spectrum.

3. Characteristics
Operating System: Android: Minimum Version 5.1 (API 22) Lolipop
Permissions: RECORD_AUDIO
Max Acquisition Rate: 44100 samples/s Number of Samples: 4096 @ 20KHz(0.05s)
Min Acquisition Rate: 2756 samples/s Number of Samples: 4096 @ 1KHz(1s)
Settings:
Run/Pause
Trigger Slider: 0 to 100% of sampled RMS value.
Time Graph Vertical Scales: 32K 16K 8K 4K 2K 1K
Freq Graph Vertical Scales: 64M 32M 16M 8M 4M 2M
Freq Graph Vertical Scales (Log): 8 7 6 5 4 3
Freq/Time Scales: 20KHz(0.05s) 10KHz(0.1s) 5KHz(0.2s) 2KHz(0.5s)
1KHz(1s)
Cursor: Off Peak Slider
Save/Email: Data writes to the following file in Pause mode:
../Android/data/com.withstrings.audioanalyzer/files. The file can also
be sent via email at the time the Save/Email button is pressed.
Inspiration: Fr. McKenzie
Crashes: Yes
© 2019 Todd Merport