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Demos Overview

The Importance of Audio Feedback

Audio feedback in a Fast Touch interface serves two main purposes.

  • It can be used to provide users with a sense of confidence that they have engaged with a device.
  • It can be used to indicate the state of system operation. A normal operating state maybe indicated by a pleasant tone or no sound, while a faulty system state could trigger an alarm.

 

Configurations

Audio Feedback in a fast touch system can be provided in three ways:

 

Features

The Fast Touch IC monitors the capacitive touch pad. Whenever, a button is actuated, the Fast Touch IC communicates with the audio feedback driver IC and chooses the desired sound to play. Upon receiving communication from the Fast Touch IC, the data stored in the sound driver IC is used to produce audio using the exciter or sometimes a separate speaker.

Designing an audio feedback system using an exciter is not a trivial process. We need to understand the noise implications of adding the extra circuitry to your fast touch interface.

We have all the tools necessary to analyze the noise created due to the audio feedback exciter and can adjust the noise algorithms accordingly. However, this extra work on our part during the prototyping stage and the extra components needed to make the interface will add cost to the final design.

      audio speaker in green

Audio Feedback Audible Feedback Exciters, Speakers and Buzzers

  • Fast Touch™ Electronics Fast Touch™ icon

    Has writing specialized software kept you from using capacitive technology? Have no fear, Fast Touch™ is here!

  • Fore Light™ Technology Fore Light™ icon

    Tired of LED hot spots ruining the look of your keypad? The search for uniform light dispersion from an LED is over!

  • Tactile Feedback tactile response icon

    Do you feel the click when pressing a button? Would you miss it if it were gone? Our research indicates: yes!

 

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The Exciter Method for Audio Feedback


Demonstration Video



An exciter placed underneath the fascia or the overlay converts the whole surface as the diaphragm of the speaker. When the exciter is stimulated, the fascia or the interface vibrates creating an audio feedback. A diagrammatic illustration of the audio feedback using an exciter is shown below:

Technical Diagram (Flow Chart)

Audio Feedback Flowchart

 

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The 8 Ohm Speaker Method for Audio Feedback


Demonstration Video

Technical Notes

Instead of turning the fascia into a speaker, we can use a standard 8 Ohm speaker to produce sound.

We designed and built this device in 1 day for a very special cause. Using our rapid prototyping capability, we gave a man suffering with ALS (Lou Gehrig’s Disease) his voice back.  To read the full article please click here!

 

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The Piezo Buzzer Method for Audio Feedback


About the Piezo Buzzer

A diagrammatic illustration of the piezo buzzer feedback method is shown below. The Fast Touch IC monitors the capacitive touch pads. Whenever, a button is actuated, the Fast Touch IC generates a PWM waveform. This waveform is fed to the piezo buzzer to produce an audible sound.

This gives the user the necessary assurance that he has engaged with the keypad.

Technical Diagram (Chart)

duty cycle chart

 

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We generally use .wav files provided by our customers to generate the required sound. However, it is important that the customers who need audio feedback note the following

Format

We require that your .wav files have a sample frequency of 4, 5.3, 6.4, 8, 12.8,16 or 32 kHz.

  • 4 kHz
  • 5.3 kHz
  • 6.4 kHz
  • 8 kHz
  • 12.8 kHz
  • 16 kHz
  • 32 kHz

Compression

Also, our audio feedback IC uses one of the following Compression Algorithms to slightly reduce the file size further and store it inside the IC.

  • µ-Law: 6, 7 or 8 bits per sample or
  • Differential µ-Law: 6, 7 or 8 bits per sample or
  • PCM: 8, 10 or 12 bits per sample or
  • Enhanced ADPCM: 2, 3, 4 or 5 bits per sample or
  • Variable-bit-rate optimized compression*

Sample

If we are able to compress a .wav file using 8KHz sample frequency and 4bit ADPCM, then we can usually get around 30 seconds of audio out of our audio driver IC. This is usually 100-105KB of data after compression.

*There might be some loss due to compression, but we can choose the compression technique that gives the best effect, while accommodating your sounds in the IC's flash memory.

 

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