About AudioSpeedGun for Tennis Serve
This app records the distance from the racket strike to the wall and the time from the racket strike to the impact sound on the wall during tennis wall practice. It calculates the initial velocity (V0) and final velocity (Vend) by applying the deceleration rate due to air resistance. While not precise, it allows you to measure approximate speed using only your smartphone. You can also save your records, so please use it for practice.

This app is a paid app, but all features except “Save,” “Log,” and “Manual Peak Selection” on the graph are available for free.

Settings
Physical parameters () are default values
[Horizontal Distance] (12.002 m)
This is the horizontal distance from the racket to the wall.
If the point of contact is closer to the wall than the court line, set this value to a shorter distance than 12.0 m.

[Racket Contact Point Height] (2.5 m)
This is the height at which the racket is swung up and the ball is struck.
For players using a jump serve, this value will be higher.

[Impact Point Height] (1.5 m)
This is the height at which the ball hits the wall.
For reference, the center of the net (center belt) is 0.914 m.

[Distance from Microphone] (2m)
This is the position of the smartphone. Internal calculations assume the device is placed on the floor, with the distance measured from the side near your feet.
If measuring with the smartphone in your pocket, please adjust the setting accordingly (e.g., 0.5m).
Do not place the smartphone near your feet or close to the ball’s landing point. Impact with the ball may cause damage to the device.
Use at your own risk.

Other: It is not usually necessary to change the sound speed (343 m/s) or the attenuation coefficient (0.012).
Analysis parameters () use default values.
[Analysis Start Time] (0 ms)
Set this if there is a lot of noise in the measurement results before the initial movement and you want to skip it.

[Noise Threshold] (50%)
In the measurement results, any level below the set maximum recording level is considered noise and excluded from peak calculation.

[Recording Time] (4 seconds)
You can select a duration between 4 and 10 seconds.

[Post-Impact Skip Time] (100 ms)
Any sound occurring within the set time after the impact sound is confirmed will be skipped as noise.

[Impact Sound Group Number] (0)
Depending on the serve style, an initial sound and multiple instantaneous impact sounds may occur.
Set which peak to consider as the impact sound.

[Group Width] (50ms)
The time duration of a single peak.

That completes the settings. Please adjust them to suit your playing style.
How to Use
AudioSpeedGun

[Start Recording]
Recording begins. There is a delay (with a countdown sound) before recording starts, as set in the timer settings.
[Stop Recording]
Stops recording. The recorded data is displayed in the graph area. Recording ends automatically based on the recording time setting.
[Start Calculation]
Performs analysis. Peaks for impact sounds and landing sounds are plotted on the graph, and the initial velocity (V0) and final velocity (Vend) are displayed.
[Details]
Displays detailed analysis results

Premium Features
(Paid)
AudioSpeedGun for Tennis Serve
[Save]
Saves data (including the settings used at the time of saving).
[Load]
Loads saved data and displays the analysis results.
[Manual Peak Selection on Graph]
On the completed analysis graph, you can drag the lines for the impact and landing sounds to any desired location.
After dragging, the system automatically selects the nearest maximum peak. Calculation results are updated in real time.

“This app is designed to work on specific OS versions at the time of release, and we do not guarantee that it will work on all future OS versions.”
https://www.picolix.jp/service.html