Ultimate speech intelligibility

Even with the noise of a blast furnace in the background

Enhanced HD Voice – eHD Voice by Commend

Since its foundation over 40 years ago, Commend has been researching and perfecting the speech quality of its systems to provide customers and users with the highest possible speech intelligibility even under the harshest conditions.

In the multi-faceted world of Intercom acoustics, everything down to the smallest influencing factor is taken into consideration when it comes to perfecting acoustic qualities – from basic physical sound properties to signal processing and the selection of individual electronic components.

In doing so, Commend keeps extending the technical frontier.

Passion for Audio by Commend

Audio Features

Hear the Difference

eHD Voice – Enhanced HD Voice by Commend transfers the audio signal at a bandwidth of 16,000 Hz, thus capturing the entire frequency spectrum of the human voice.

Please note: The quality of the audio samples depend on the quality of your PC speakers.

Audible range

20 Hz
3,500 Hz
7,000 Hz
16,000 Hz
20,000 Hz


The basic audio bandwidth is 3.5 kHz. This is what we are all familiar with on the telephone. Overall, 80 percent of the sound frequencies involved in speech transmission are beyond the capabilities of the public telephone standard.


7 kHz quality means a clear improvement in clarity and intelligibility. However, this still covers less than 50% of the audible frequency range. Critical frequencies that are needed for consonant differentiation are still missing.


Enhanced HD Voice by Commend transfers the audio signal at a bandwidth of 16,000 Hz, thus capturing the entire frequency spectrum of the human voice. As a result, voice communication and emergency calls are transmitted at a level of clarity literally unheard-of so far.

  • OpenDuplex® – Commend Standard for natural conversation experience since 2003 – simultaneous loud speaking and listening. More
  • STI (Speech Transmission Index) 0.96 – measured under acoustic laboratory conditions; STI is a standard measure for speech intelligibility. It has a possible maximum value of 1.00, which corresponds to perfect intelligibility.
  • Clear voice transmission at high volumes with intelligent volume control (IVC) to ambient noise conditions. More
  • Dynamic background noise suppression virtually eliminates all ambient noise.
  • Loudspeaker/microphone monitoring – ensures the availability of the Intercom station while reducing the need for manual verification of its functionality. More
  • Audio Monitoring – user security with support for fully automated system actions (e. g., emergency call) at defined noise levels. More
  • Public Address functions
  • Audio recording and lip synchronous Audio/Video recording of conversations for documentation and evidence keeping purposes. More
  • Peer2Peer Audio reduces network and server load to ensure efficient use of resources.
  • Conference Call function for simultaneous talking with multiple conversation partners.
  • Speech activity detection senses when calls are finished (no microphone signal) and terminates the connection automatically.
  • Simplex mode for applications requiring controlled communication – e.g., security solutions based on the ‘push-to-talk/release-to-listen’ method. More
  • Equalizer for fine-tuning Intercom stations to ambient acoustic conditions.