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Copyright & Disclaimer:
Copyright: This publication, including all photographs and illustrations is protected under
international copyright laws, with all rights reserved. Neither this manual, nor any of the material
within, may be copied or reproduced without the written consent of bhi Ltd.
Disclaimer: The information in this document is subject to change without notice. bhi Ltd. makes no
representations or warranties with respect to the contents hereof and specifically disclaims any
implied warranties of merchantability or fitness for any particular purpose. Furthermore, bhi Ltd.
reserves the right to revise this publication and to make changes from time to time in the content
hereof without obligation of bhi Ltd. to notify any person of such revision or changes.
1. Introduction
The NEDSP1901-PCB module is an audio DSP noise cancelling module that is used to clean up noisy
speech signals to give improved speech clarity in noisy conditions. The 1901 module is pin for pin
replacement module for the discontinued NEDSP1061-PCB module. It operates with a similar
specification but incorporates the latest bhi DSP noise cancelling technology and maintains virtually
the same physical dimensions as the NEDSP1061-PCB.
1.1 NEDSP 1901 Module Features:
•
Fully adaptive to changing noise environments
•
Input and output level controls
•
Virtually no distortion to speech signals
•
Up to 40 dB noise reduction in 8 selectable levels
•
Audio bandwidth 300Hz to 5KHz
•
Noise Reduction may be preset or remotely set during operation.
•
7 to 18 Volt supply range
•
Approximately 10 dB of signal gain with the ability to drive impedances of less than 1KOhm.
•
Wide range of connection possibilities
•
Mounting holes
1.2
Limitations
This module is designed to pass speech. Other signals such as data, music and morse (CW) will, to
some degree pass through, but the integrity of these signals cannot be guaranteed. Like the
NEDSP1061-PCB module it is designed to be placed in a low-level audio path (up to 1V p-p) only,
NEDSP1901-PCB User Manual Iss A
DSP side of PCB
www.bhi-ltd.com
Rear side of PCB
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Summary of Contents for BHI NEDSP1901-PCB
- Page 1 Ltd. to notify any person of such revision or changes. 1. Introduction The NEDSP1901-PCB module is an audio DSP noise cancelling module that is used to clean up noisy speech signals to give improved speech clarity in noisy conditions. The 1901 module is pin for pin replacement module for the discontinued NEDSP1061-PCB module.
- Page 2 although there is a level adjustment on the module which will require adjustment. The output will not drive a loudspeaker or other high-power load. 1.3 Module connection and Mounting Connections to the module are made by a row of 10 plated through holes to one end which form PL2.
- Page 3 An on-board voltage regulator allows the module to be used with a wide range of input voltages, but to keep the power dissipation (and heat) down, it is advisable to use as low as possible supply voltage. The power supply input is reverse polarity protected. 1.4 DSP Noise Reduction The NEDSP1901 processes the incoming signal and uses known speech and noise patterns to differentiate the speech from the noise.
- Page 4 2.0 Module Description 2.1 Block Diagram The NEDSP 1901 module has the facility to be preset or adjusted during operation. Digital input control the functions. These incorporate internal pull-up resistors so they can be left floating when not in use. The audio signals into and out of the module are capacitor coupled to ensure that no DC levels are pulled down or shorted when the module is used embodied as part of existing equipment.
- Page 5 2.2 Module Layout Figure 3 below shows the board dimension detail as seen from above. The overall thickness of the board is 8.75mm. When considering the installation of this module, at least 9.5 mm height should be provided, which will allow for the clearance of through-hole solder pins. Figure 3.
- Page 6 2.3 Pin Functions The basic operation of the NEDSP pins are described below. More details may be found later in this manual. Pins 1-3 DSP Filter level set -These pins allow remote setting of the noise cancellation level. If these pins are used, then ensure that the appropriate on-board pre-set solder jumpers are removed (JP1 –...
- Page 7 2.5 Electrical Characteristics Output impedance: 1k Ohms typical Input impedance: 7.5k Ohms typical Analogue Characteristics Parameter Description Min. Typ. Max. Units Supply Voltage Supply Current Audio Input Signal mV (rms) Audio Output Signal 1000 Digital Characteristics Parameter Description Min. Typ. Max.
- Page 8 4.0 Functions 4.1 Noise Reduction Levels 8 Levels of noise reduction are available. Noise and tone reduction is shown in the table below: Level Tone Reduction White Noise Reduction 12dB 16dB 20dB 16dB 25dB 21dB 30dB 25dB 35dB 65dB 40dB Notes: 1.
- Page 9 4.4 Setting the Noise Reduction Level using the On-board Jumper links The on-board Noise reduction selection jumper selectors are located on the underside of the Module as shown below. These jumpers are actually PCB pads that should be linked using a solder bridge.
- Page 10 5. Application Notes 5.1 Noise Cancellation On/Off with indication In the example opposite a Tricolour (or separate Red and Green) LED’s are used to give a visual indication of the Noise Reduction mode. The Green LED will illuminate when the Noise Reduction is On and the Red will illuminate when the Noise Reduction is Off.
- Page 11 The module can be controlled with a microcontroller. It is not necessary to drive the control pins with the controller as the NEDSP has internal pull-up resistors. Therefore, the microcontroller would operate pulling Low or in a High impedance state. Figure 10 –...
- Page 12 Contact details: bhi Ltd PO Box 318 Burgess Hill West Sussex RH15 9NR Tel: +44 (0)1444 870333 Email: sales@bhi-ltd.com Web: www.bhi-ltd.com...
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