Prospec real time spectrum analyzer user manual

ProSpec – Real Time Spectrum Analyzer User Manual [PDF]
ProSpec is a professional real-time acoustic spectrum analyzer for mobile devices running Android version 2.3.4 and above available on the Google Play Market. ProSpec lite is also available to try for free here. Some of the features include:

  • Real time spectrogram generation
  • Real time amplitude generation
  • Selectable sampling frequency from 8-kHz to 44.1kHz
  • Selectable frequency resolution from 64-1024 bands (in powers of 2)
  • Selectable Analysis frame duration (10ms – 100ms)
  • Selectable Analysis window (Hamming, Hanning, Rectangular, Blackmann)
  • Instantaneous SPL with calibration (Device dependant)
  • Maximum frequency tracking
  • Real time Spectrum Zoom feature
  • On screen playback after recording
  • Snap shot and share spectrogram
  • Save and share audio
  • Off-line audio analysis (Playback and full spectrogram analysis of the previously recorded audio)
  • Selectable dynamic range for all spectrograms
  • Selectable colour for display
  • Invert feature for dark environments

Feel free to join the discussion group to discuss new features, bugs, trouble shooting or ideas. The remainder of this post describes how to use ProSpec analyzer on an Android device. To quickly learn how to do a particular action, below is contents of this user manual, choose the required chapter and navigate to the associated number.

  1. Main Screen Elements and Navigation
  2.  Recording, Saving and Sharing Audio
  3.  Zooming, Saving and Sharing Spectrograms
  4.  Entire Spectrogram Analysis and Playback
  5.  System Preferences
  6.  Tell Your Friends

1. Main Screen Elements and Navigation

User Interface for Prospec

User Interface for Prospec

Fig 1. Main UI

Main elements illustrated in Fig 1.

A. Primary Real-time Spectrogram view, displaying time and frequency content of recorded audio
B. Real time amplitude gauge , displaying the energy of the recorded audio
C. Energy scale measured in dBFS
D. Instantaneous frequency tracker and Maximum frequency display in dBA (SPL)
E. Top user control panel for saving, sharing and other options
F. Main user control panel for recording


Prospec button locations

Prospec button locations

Fig2. Button Locations

Key buttons to know about illustrated in Fig 2:
A. Record / Stop recording
B. Zoom
C. Reset spectrogram, resets the spectrogram to zero online and offline
D. Application settings
E. Pause / Resume recording
F. Quick settings slide out menu
G. Social network connectivity
H. Audio and Image tools
I. Play / Stop button (Only when recording is stopped)

Prospec quick settings menu

Prospec quick settings menu












Fig 3. Quick settings menu
Quick settings menu
A. Color theme options
B. Sampling Frequency adjustments
C. Spectrogram Dynamic range control
D. Update speed
E. Advanced spectrogram settings
F. Sound Pressure Level (SPL) calibrations
G. View current spectrogram configuration
H. Close
Outline of sub menus
A. Color sub menu, Fig 3 shows the color options. “RGB” uses the Jet color scheme similar to the one in
Matlab. “Pick a color” open up a new dialogue (Fig 3. bottom) allowing you to choose any color for the

spectrogram and over all theme. “Invert” inverts everything to be black as the background.


Prospec Color pallet

Prospec Color pallet












Fig 4. Color pallet
B. Fs sub menu, Fig 4. Shows the sampling frequency options dialogue

Prospec sampling frequency options

Prospec sampling frequency options









Fig 5. Sampling Frequency options
E. Advanced sub menu, Fig 6. Shows the Advanced spectrogram settings, here there are one sliding bar and four main settings buttons, which are:

  1. Sliding bar: allowing you to change the window length between 10-100ms
  2. Analysis Window: Change the analysis window type (Shown in Fig 5. middle)
  3. FFT Length: Change the FFT resolution (Shown in Fig 5. Bottom)
  4. Reset Defaults: Resets window length to 32ms, Analysis window to Hamming and FFT size to 1024
Prospec's advanced spectrogram settings

Prospec’s advanced spectrogram settings












Fig 6. Advanced Spectrogram Settings

F. SPL Calibration sub menu. Fig 7. shows the SPL calibration dialogue. An offset of 0dB is my current
calibration for a Motorola Atrix running Android 2.3.4. However, your device will no doubt be different
and hence will display the incorrect value. To calibrate follow these steps:


Sound Pressure Level Calibration

Sound Pressure Level Calibration







Fig 7. SPL Calibration

  1. Acquire an SPL meter, like one of the recommended ones below, turn it on and ensure it is on A-weighting.
  2. Find a constant sound source and record with ProSpec, while monitoring with the SPL meter.
  3. Note the dBA value of the SPL meter and the dBA value on ProSpec
  4. Calculate the difference
  5. Adjust the calibration according to the difference.

*NOTE: This is by no means an accurate measure (Even calibrated), I have only included it as I wanted to get a ball park figure on the SPL of things, it is highly device dependant.

G. View Config sub menu: Fig 8. shows the current spectrogram settings, these can used to describe the spectrogram at any time, useful for demonstration purposes. So you can always say this spectrogram has been generated with these settings.

Spectrogram configuration

Spectrogram configuration









Fig 8. Spectrogram Configuration
2. Recording, Saving and Sharing Audio
Start recording:

Record and pause

Fig. 9, Record and Pause buttons



In Fig. 9, press the left (Bottom left hand side) to begin recording. The button will toggle and the green circle will become red with a microphone cutout to indicate that ProSpec is currently recording from the microphone. The audio file cannot be listened to, saved or shared until recording has been completed.

Stop recording:
To stop recording press the record again and the button will toggle back to a green state. This means recording is complete, now you can play, save or share the audio.


Ppausedause Recording:
If for whatever reason you want to momentarily pause recording, you can do so by press the left button in Fig. 9, this will pause recording if recording is activated. If you press stop recording while paused the pause state will be reset, otherwise to resume recording press button E again.

Saving your recording:
When you have finished recording, ProSpec has finished writing to the file called prospec.wav found on the sdcard or internal memory in the directory ProSpec. You can, however, save this wav file to a location of your choice by pressing the speaker button shown in Fig 10. Several options will appear shown, press “Save” and a file browser will open shown in Fig 10. and you can browse to the desired folder or create a new folder.







Fig 10. Audio options







Fig 11. Saving wav file

Sharing the Audio
To share the audio you can press “Share” in Fig 10. and a list of supported sharing services already installed on your device will open. Typically this feature is used if you want to e-mail a recording to someone or yourself.

3. Zooming, Saving and Sharing Spectrograms

Real time zooming:
When recording you can zoom in and observe specific frequencies of interest, this is achieved by selecting the magnify button in the bottom centre console shown in Fig 12. A new window will appear allowing you to specify the frequency region of interest shown in Fig 13. If the lower frequency (left) is higher than the upper frequency (right) then a warning will flash on the screen, and pressing ok  will have no effect. The upper frequency will only be as high as the maximum frequency possible for the specified sampling frequency (See section 1). For further assistance press the “Help” button shown in Fig 13.




Fig 12. Bottom console








Fig 13. Zoom frequency selector

Additionally, after the recording has been completed you can view the spectrogram in any image viewer/image editor that you already have installed on your device. To do this press the camera in the top right hand corner (Shown in Fig 14.) and select “View” and a list of supported services will open.

Saving the Spectrogram
You can save a snapshot of the spectrogram during recording by pressing the camera on the top right hand side and selecting “Save” shown in Fig 14. And a file browser will open allowing you to  navigate, create new folders and name the PNG file to be saved.











Fig 14. Snap shot menu

Sharing the Spectrogram
If you want to send the current snapshot to your home computer or share it to a friend you can do so by pressing the camera again (As done in saving the Spectrogram) and selecting “Share”. Two options will appear on the screen (Shown in Fig 15), allowing you to share directly to your Facebook wall or via e-mail using any supported client already installed on your device.




Fig 15. Share Spectrogram

4. Entire Spectrogram Analysis and Playback

ProSpec contains another very powerful feature which will eventually also be a standalone app, this feature is designed to sustainably handle to viewing the spectrogram and playback of audio for an entire sequence whether it be 10 seconds or 10 minutes in length without compromising on the quality of the spectrogram (e.g. resolution or image compression). This is useful if the time lapses past the end of the screen and the new spectrogram over writes the old spectrogram and you would like to take another look at the spectrogram in the past. To access this tool, selecting the speaker button on the  top right hand side (Shown in Fig 9.) and select “Listen” after you have finished recording. This will open a new view with a loading dialogue. The dialogue is simply loading a time-energy plot of the entire audio sequence you have recorded. Fig 16 shows the main listen user interface (UI), and below is list of each element:

A. Audio play back progress bar
B. Main control console for media playback and other settings
C. Spectrogram drawing area
D. Time-Energy selection tool








Fig 16. Main UI for the listen tool
In Fig 17, the buttons and other interactive components are outlined, and below are their descriptions








Fig 17. Listen Buttons
A. Snap shot tool allowing you to share, save and view the current spectrogram, sub menu shown in Fig 18






Fig 18. Snapshot options
B. Main audio controls, allowing you to play, pause, stop, repeat fast forward or rewind
C. Spectrogram analysis segment settings, allowing you to change the analysis segment between 10-30 seconds, sub menu shown in Fig 19.






Fig 19.  Analysis segment length
D. Interactive spectrogram window, allowing you to drag the window to any region of the waveform, window duration set by C. default is 10 seconds
E. Playback progress bar, also allowing you to select anywhere to play from
5. System Preferences
To access system preferences press the toolkit located in the bottom console shown in Fig 20.



Fig 20. System preferences Button

The system preferences screen opens shown in Fig 21. Here you can keep the screen awake, reset factory defaults or remove all generated files.








Fig 21. System preferences
6. Tell your friends
Fig 22. shows how to access social interaction controls of ProSpec, although not necessary it would be greatly appreciated if you have had a positive experience to help spread the word using these controls. Here you can chat to other users, including myself and share ProSpec with friends on twitter and facebook. This will help me in my self funded journey researching signal processing techniques to improve hearing for those with profound hearing loss, namely cochlear implant patients. For more information on ProSpec or my cause you can e-mail me on “miscanalysis at gmail dot com” or sponsor me with Gitip.





Fig 22. Social interaction menu