Very low consumption and radiation softphones

Short Title
Very low consumption and radiation softphones.

Long Title
Very low consumption and radiation softphones, with the support of the spatial audio, of the frequency shifts and of the ultrasonic communications.

Short Description
Mobile phone apps to promote an audio codec (audio compression and decompression method) characterized by its simplicity, its low bitrate and its low audio frame emission frequency.
With the support of the spatial audio, of the frequency shifts and of the ultrasonic communications.

Long Description

vlrPhone is an app based on PJSIP and Open Source products, whose goal is to promote, in the future versions, a new codec (compression and decompression method) for the audio and the ultrasounds.
This codec is based on FFT (Fast Fourier Transform), the greatest points and the most energetic bands. It can also use only the local peaks.
This codec is characterized by its efficiency, its simplicity and its robustness.
It will allow low battery consumption (VLC, Very Low Consumption, yellow button) and emissions of audio frames limited to the strict minimum, so the electro-magnetic radiations will be minimized (VLR, Very Low Radiation, green button).
It will allow, in real-time, the frequency shifts, the pitch shifts and the equalization for the correction of hearing losses.
It will allow also to do local or near-field ultrasonic communications, so with no electro-magnetic radiation, with or without frequency shifts.
If the codec is not implemented, the app behaves as a normal softphone.
If the correspondent does not use vlrPhone, the app behaves as a normal softphone.
For more information:
- Frequency Shifting
- Pitch Shifting
- Audio Equalization
For the reduction of noise or the elimination of moderate noise when receiving noisy communications, highly efficient algorithms compatible with the VLC and VLR codecs have been developed.
For more information:
- Noise Reduction
Lastly, vlrPhone will allow the support of the spatial audio also called 3D positional audio.
For more information:
- 3D Positional Audio

Asterisk Module

In order to use the VLC and VLR codecs with correspondents not using these codecs, it is planned to develop a module for the Asterisk server.
Asterisk is a very popular VoIP server which is able to perform the necessary transcoding with the standard audio codecs.
This server is Open Source, runs on a PC under Linux and also uses the PJSIP library. The development of this module should therefore not pose too many problems.
For more information about the Asterisk server, see:
- Asterisk Server

The VLC and VLR codecs and the Ultrasounds

VlrPhone uses a codec (or rather a family of codecs) compatible with the ultrasounds.
These codecs can take the ultrasounds into account in three ways:
- By increasing the useful audio band. Beyond 20 kHz, the sounds become inaudible for the human ears and are called ultrasounds.
- By taking into account only the areas in the ultrasound.
- By performing frequency shifts towards the ultrasounds.
For more information:
- Ultrasounds Support

The Spatial Audio with the Bone Conduction Systems

The osteophony or the bone conduction refers to the phenomenon of propagation of sound to the inner ear via the bones of the skull.
Some headphones use the bone conduction, and reproduce an effect equivalent to direct listening.
A headphone is positioned ergonomically on the temple and cheek, and the electromechanical transducer converts electrical signals into mechanical vibrations, sending the sound to the inner ear through the bones of the skull.
Similarly, a microphone can be used to record sounds spoken by the bone conduction.
There are three categories of products:
- Ordinary products, such as hands-free headsets or headphones.
- Bone-anchored hearing aids and assistive listening devices.
- Specialized communication products (e.g. for underwater or high-noise environments).
The main advantages are:
- The ears are in the open air, thus offering more comfort and allowing a prolonged use, in total safety.
- The devices offer high sound clarity in very noisy environments, and can be used with a hearing protection.
- They also allow the perception of sounds in stereophony.
The main disadvantages are:
- Some implementations require more power than the standard headphones.
- The frequency bands are smaller than for the standard headphones, so the recordings and the readings are less clear.
For more information:
- Bone Conduction
The bone conduction headphones do not pass through the outer ear or through the middle ear, and therefore are not sensitive to the spectral filters due to these organs.
Spectral filters are responsible in particular of the elevation localization.
With vlrPhone, we will be able to use customized HRTF (Head-Related Transfer Function) filters, usable with the bone conduction headphones, in binaural listening.
The HRTF filters will be applied just before decompression and can be changed dynamically (e.g. to take into account of the head movement).
For more information on the spatial audio or 3D positional audio, see at the following address:
- 3D Positional Audio
The HRTF filters can be used to place an audio source at a given position (instead of, for example, between the two ears, in the middle of the head).
They can also be used to create virtual speakers around the user for a binaural listening via stereo headphones.
The bone conduction headphones can be seen as audio augmented reality headphones. Indeed, these headphones leave the ears in the open air, in contact with the real sound.
Since the ears have a 3D spatial perception of the sound, it is important to be able to homogenize, harmonize or personalize the sound perception with the bone conduction headphones.

The Ultrasounds Transmitted by the Bone Conduction

The ultrasounds transmitted by the bones are also called BCU, or Bone-Conducted Ultrasound.
The Scientists have long known of the ability to hear ultrasonic frequencies (between 20 and 100 kHz).
The ultrasounds are audible by the bone conduction. Some deeply deaf subjects (including sensory deafness) as well as subjects with normal hearing can hear and understand BCU whose amplitude is modulated by the voice.
With the AM-BCU or amplitude-modulated BCU, the voice and the music can be heard and understood by:
- subjects with normal hearing,
- some deeply deaf subjects,
if the signal is correctly shifted (towards the high frequencies and the ultrasound) and transmitted to the body.
In the time domain, the amplitude modulation consists in multiplying the signal to be modulated (audio signal) with the carrier signal (of higher frequency).
In the temporal domain there is a multiplication of the signals, so in the frequency domain there is a convolution.
Since the carrier signal consists of only one frequency, the spectrum of the modulated signal is equal to the audio spectrum shifted towards the frequency of the carrier.
The result is a modulated spectrum composed of three components: a carrier wave, an upper sideband and a lower sideband.
This shift can be performed instantly by the vlrPhone software just before decompression.
The vrlPhone software will offer this feature for the 48 and 96 kHz sampling rates.
The user will be able to choose the frequency of the carrier, for example 10, 20 or 30 kHz. The modulated signal will to be transmitted to bone conduction systems having an adequate bandwidth.
The amplitude of the carrier will also be able to be changed.
For the voice communications, the bitrates will be able to be as low as for the 8 or 16 kHz sampling rates.
It will be still possible to apply the HRTF filters to the signal to be modulated before the modulation and the decompression, but the results will not be as expected since the mechanisms of the AM-BCU are not yet clearly known and the inner ear seems not to play an important role.


The project is led by the manager of the WhmSoft company, a limited liability society. The latter is a professional developer and webmaster (C/C++, PHP/MySQL, HTML5/CSS3/JavaScript/jQuery, ...).
He developed the WhMic software (running on Windows, program) in which there is a codec called WHM Voice that will be used for VLC.
He maintains the following web sites:

The objectives are:
- Programming of the codec (VLC and VLR versions) for Windows with an Open Source softphone (GreenJ).
- Programming of the codec (VLC and VLR versions) for Android with an Open Source softphone (GreenJ or CSipSimple).
- Programming of the codec (VLC and VLR versions) for iOS (iPhone / iPad) with an Open Source softphone (GreenJ or Siphon).
- Promotion of the codec in order to be used the most widely possible.
The sources will be available for the developers.

The project is divided into four distinct parts:

1) Program VLC and VLR for Windows.
2) Program VLC and VLR for Android.
3) Program VLC and VLR for iOS.
4) Promotion of the codec.

This fundraising is for the three first parts (programming).
The contributors will have obviously free access to all apps as they become available.
A portion of raised funds will be used to buy and send the counterparties promised to contributors.

Address of the web page of the apps:
On can find on this page additional information, including more details on the algorithms to be used.
The possible Android app with the final user interface is available on Google Play at the following address:
This app does not yet contain the codec but can be used as a normal softphone.

The project has a very significant impact in everyday life:
- It will help to greatly reduce the battery consumption during the voice communications, if the two correspondents use the codec.
- It will allow, in real-time, the frequency shifts, the pitch shifts and the equalization for the correction of hearing losses.
- It will allow the support of the spatial audio also called 3D positional audio.
- It will help to reduce the audio frames emissions, so the electro-magnetic emissions.
Discussions are currently taking place between experts to know if the effects of these waves are carcinogenic in the long term or in case of intensive uses of mobile phones.

You can also support the project:
- By downloading and using the apps.
- By signaling the project around yourself.
- By sharing your observations and reporting the problems.

See on the crowdfunding website.