Microphone Housing
Microphone Housing
DESIGN NOTE
Microphone Housing Considerations
Proper design and consistent manufacturing of the microphone housing is important as improper acoustic
positioning of the microphone will reduce recognition accuracy.
This section describes several important considerations that must be carefully followed in designing the
microphone mounting and housing. Many mechanical arrangements are possible for the microphone element,
and some will work better than others. Sensory recommends the following guidelines for designing the
microphone housing:
FIRST: In the product, the microphone element should be positioned as close to the mounting surface as
possible and should be fully seated in the plastic housing. There must be NO airspace between the microphone
element and the housing. Having such airspace can lead to acoustic resonance, which can reduce recognition
accuracy.
Good:
Bad:
Mic. element flush with surface
Air cavity between mic. element and surface.
Figure 1 -- Microphone Mounting (1)
© 2006 Sensory Inc.
P/N 80-0258-C
1
Design Note
Microphone Housing
SECOND: The area in front of the microphone element must be kept clear of obstructions to avoid interference
with recognition. The diameter of the hole in the housing in front of the microphone should be at least 5 mm. Any
necessary plastic surface in front of the microphone should be as thin as possible, preferably no more than 0.7
mm.
nothing here!
surface
mic. element aperture
mic. element diaphragm
Figure 2 -- Microphone Mounting (2)
THIRD: The microphone should be acoustically isolated from the housing if possible. This can be accomplished
by surrounding the microphone element with a spongy material such as rubber or foam. Mounting with a nonhardening adhesive such as RTV is another possibility. The purpose is to prevent auditory noises produced by
handling or jarring the product from being “picked up” by the microphone. Such extraneous noises can reduce
recognition accuracy.
Good:
Bad:
Absorbent material surrounding element.
Element fastened directly to housing.
Absorbent material
(usually rubber or foam)
Product housing
(usually plastic)
Figure 3 -- Microphone Mounting (3)
NOTE: If the microphone is moved from 6 to 12 inches from the speaker’s mouth, the signal power decreases
by a factor of four. The difference between a loud and a soft voice can also vary by more than a factor of four.
The internal preamplifier of the RSC-4128 compensates for a wide dynamic range of input signal strength, but if
its range is exceeded, software can provide auditory feedback to the speaker about the voice volume. The
product can achieve this by saying such as “please talk louder” or “please don’t talk so loudly.
2
P/N 80-0258-C
© 2006 Sensory Inc.
Design Note
Microphone Housing
The Interactive Speech™ Product Line
The Interactive Speech line of ICs and software was developed to “bring life to products” through advanced speech
recognition and audio technologies. It is designed for cost-sensitive consumer-electronic applications such as home
electronics, home automation, toys, and personal communication. The product line includes the award-winning RSC-4x
general-purpose microcontrollers and tools, the VR Stamp™ 40 pin DIP module and tools, the SC series of speech and
music synthesis microcontrollers. Our suite of software development kits are designed to run on non-Sensory processors
and DSP’s, and support most popular operating systems.
RSC Microcontrollers and Tools
The RSC product family contains low-cost 8-bit speech-optimized microcontrollers designed for use in consumer electronics.
All members of the RSC family are fully integrated and include A/D, pre-amplifier, D/A, ROM, and RAM circuitry. The RSC
family can perform a full range of speech/audio functions including speech recognition, speaker verification, speech and
music synthesis, and voice recording/playback. The family is supported by a complete suite of evaluation and development
toolkits.
Speech Recognition Modules and Tools
The VR Stamp™ is a complete speech recognition module based on the RSC-4x and is ideal for fast design and easy
production. A low-noise audio channel and standardized 40-pin DIP footprint allow rapid prototyping, less debugging, and
shorter time to market. The VR Stamp Toolkit includes everything needed to get started today, including VR Stamps, Module
Programming Board, sample applications, and a complete set of development tools featuring the Phyton IDE and limited-life
C compiler, QuickSynthesis™ 4 and Quick T2SI-Lite™ speech tools.
SC Microcontrollers and Tools
The SC-6x product family features the highest quality speech synthesis ICs at the lowest data rate in the industry. The line
includes a 12.32 MIPS processor for high-quality, low data-rate speech compression and MIDI music synthesis, with plenty
of power left over for other processing and control functions. Members of the SC-6x line can store as much as 37 minutes of
speech on-chip and include as many as 64 I/O pins for external interfacing. Integrating this broad range of features into a
single chip enables developers to create products with high quality, long duration speech at very competitive price points.
FluentSoft™ Technology
FluentSoft™ Recognizer is the engine powering the FluentSoft™ SDK. It provides a noise-robust, large-vocabulary, speakerindependent solution with continuous digit recognition and word-spotting capabilities. This small-footprint software
recognizes up to 5,000 words; runs on non-Sensory processors including Intel XScale, TI OMAP, and ARM9 platforms; and
supports operating systems such as MS Windows, Linux, and Symbian.
3Dmsg™ Technology
3Dmsg’s (www.3Dmsg.com) Animated Speech technology offers animated avatars with advanced speech recognition and
synthesis capabilities for use in smartphones, language trainers, and kiosk applications. Facial expressions can be
configured to show emotions and lip synchronization can be automatically driven from voice or text data.
Important notices:
Sensory Incorporated (Sensory, Inc.) reserves the right to make changes, without notice, including circuits, standard cells, and/or software,
described or contained herein in order to improve design and/or performance. Sensory, Inc. assumes no responsibility or liability for the use
of any of these products, conveys no license or title under any patent, copyright, or mask work right to these products, and makes no
representations or warranties that these products are free from patent, copyright, or mask work right infringement, unless otherwise
specified. Applications that are described herein for any of these products are for illustrative purposes only. Sensory, Inc. makes no
representation or warranty that such applications will be suitable for the specified use without further testing or modification.
Safety Policy:
Sensory, Inc. products are not designed for use in any systems where malfunction of a Sensory, Inc. product can reasonably be expected to
result in a personal injury, including but not limited to life support appliances and devices. Sensory, Inc. customers using or selling Sensory
Incorporated products for use in such applications do so at their own risk and agree to fully indemnify Sensory, Inc. for any damages
resulting from such improper use or sale.
575 N. Pastoria Ave., Sunnyvale, CA 94085
Tel: (408) 625-3300
Fax: (408) 625-3350
© 2006 SENSORY, INC. ALL RIGHT RESERVED.
Sensory is registered by the U.S. Patent and
Trademark Office.
All other trademarks or registered trademarks are the
property of their respective owners.
www.sensoryinc.com
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