Category: Music
SPL Graph

SPL Graph

       iOS Universal

SPL Graph is an audio Sound Pressure Level (SPL) chart recorder. It includes:

* Plot sound level over time
* Record audio while plot is running
* Do octave and 1/3 octave band analysis (optional)
* Show a 3D Plot of octave or 1/3 octave results (optional)
* Calculate Ln SPL values
* Email notifications when sound exceeds limits
* Auto-save results after set intervals, and email the results to you
* Start another plot after auto-saving for continuous operation

SPL Graph works by averaging the SPL for one second, applying an optional weighting filter, and plotting the sound level, recording the raw audio signal, if recording is turned on.

The app works very well with the built-in iOS device microphone. To upgrade the app to true pro standards, add our iTestMic or iAudioInterface2 with a microphone, and get ANSI or ISO Type 1 o2 2 results.

SPL Graph can record up to 24 hours of sound level data, with single second resolution. The graph starts with a one-minute plot window, and as a minute is recorded, the graph re-scales automatically and adds another minute to show the data collected so far. The overall SPL leve, or LEQ, is displayed for whatever portion of the test is showing on the graph.

Tap the play button to play back the recorded audio, and you can use the cursor to scrub the audio location on the graph. Use this feature to listen to events that you can see on the graph.

With the optional octave logging module, you can also record the octave or 1/3 octave band levels. And, you can view the data on the 3D plot for a graphical view of frequency over time.

You can scroll and scale the graph vertically, in dB, by using standard swipe and pinch gestures. You can also scroll and expand and contract the time axis using gestures. Zoom out to a full 24 hours, or zoom in to a single minute, showing second resolution. Double-tap the screen to zoom out to show the entire graph on the screen.

The time scale grid changes dynamically, highlighting minutes, ten-minute, and hour lines as as it runs.

As the graph runs, the overall LEQ (average SPL) for the entire time period is computed and displayed on the screen. Swiping across the graph brings up a cursor that displays the exact dB level and time for any point on the graph.

You can turn on audio recording, so that you have a record of the sounds that were happening while the graph was being stored. You can use this to figure out exactly what the sound was that caused a peak on the graph, for example. Recordings can be compressed or uncompressed.

If you exit the app, or are interrupted with a phone call, the graph data will not be lost. SPL Graph will automatically save the graph, and reload it when you next open the program. You can also save a graph in one of ten files on the iPhone, so that you can recall the graph later.

SPL Graph supports saving graphs directly on your iOS device. You can recall these graphs and bring them up on the screen, and listen to the sounds that were made while the graph was recorded. You can also store an image of the screen to your photo roll. Use Dropbox or iTunes Files Sharing to export the results to your computer.

You can also export data in tab-delimited files for XLS import. Dropbox is supported for automatic file transfer.

The filters are all ANSI type 1 or better, and include A-weighting, C-weighting, and all octaves band filters from 32 to 16kHz.

Like all Studio Six Digital audio apps, SPL Graph supports calibration. The app ships calibrated for the iOS device that it is running on. If you have access to a calibrated SPL meter you can calibrate your iPhone.

NOTE: This app was renamed from "LEQ Graph".

Also, see our other great audio and acoustical analysis apps: AudioTools, SPL, SPL Meter, RTA, ETC, RT60, FFT, Generator, and Speaker Pop.

What's new

** Bug fixes and stability improvements.
** Improved calibration system to handle multiple headset, USB audio, and iAudioInterface2 microphones.


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Last changed:
Jun 13, 2014
Andrew Smith
23.0 MB

Current Version Average Rating:
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All Versions Average Rating:
4.50 (22)
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SPL Graph 4.50 out of 5 based on 22 ratings.