BRUEL & KJAER 4720 Guide

Technical
Documentation
HEADQUARTERS: Brüel & Kjær Sound & Vibration Measurement A/S ·DK-2850 Nærum ·Denmark
Telephone: [phone] ·Fax: [phone] ·www.bksv.com ·[e-mail]
Local representatives and service organisations worldwide
Echo Speech Source Type 4720
English BE 1866– 11
User Manual
ËBE-1866---MÎ
BE1866-11_Cover.fm Page 1 Wednesday, December 18, 2013 11:22 AM

BE 186611 December 2013
Echo Speech Source
Type 4720
User Manual

Copyright 2013, Brüel & Kjær Sound & Vibration Measurement A/S
All rights reserved. No part of this publication may be reproduced or distributed in any form, or
by any means, without prior written consent from Brüel & Kjær Sound & Vibration Measurement
A/S, Nærum, Denmark
Safety Considerations
This apparatus has been designed and tested in accordance with IEC/EN 61010 – 1 and
ANSI/UL 61010 – 1 Safety Requirements for Electrical Equipment for Measurement,
Control and Laboratory Use. This manual contains information and warnings which must be
followed to ensure safe operation and to retain the apparatus in safe condition. Special note should
be made of the following:
Safety Symbols
The apparatus will be marked with this symbol when it is important that you refer to the
associated warning statements given in the manual.
Protective Earth Terminal Hazardous Voltage
Explosion Hazard
The equipment is not designed to be used in potentially explosive environments. It should not be
operated in the presence of flammable liquids or gases.
Warnings
• Switch off all power to equipment before connecting or disconnecting their digital interface.
Failure to do so could damage the equipment
• Whenever it is likely that the correct function or operating safety of the apparatus has been
impaired, it must be made inoperative and be secured against unintended operation
• Any adjustment, maintenance and repair of the open apparatus under voltage must be
avoided as far as possible and, if unavoidable, must be carried out only by trained service
personnel
• Do not dispose of electronic equipment or batteries as unsorted municipal waste
• It is your responsibility to contribute to a clean and healthy environment by using
the appropriate local return and collection systems
• Hazardous substances in electronic equipment or batteries may have detrimental
effects on the environment and human health
• The symbol shown to the left indicates that separate collection systems must be used
for any discarded equipment or batteries marked with that symbol
• Waste electrical and electronic equipment or batteries may be returned to your
local Brüel & Kjær representative or to Brüel & Kjær Headquarters for disposal

Table of Contents
CHAPTER 1
Introduction......................................................................................................... 1
1.1 Before First Use ................................................................................................... 1
CHAPTER 2
Overview.............................................................................................................. 3
2.1 Control Panel and Loudspeaker .......................................................................... 3
2.2 Battery Compartment........................................................................................... 5
2.3 Tripod Mounting Plate.......................................................................................... 5
CHAPTER 3
Installation........................................................................................................... 7
3.1 Installing the Echo Speech Source Software....................................................... 7
3.2 Batteries............................................................................................................... 7
3.3 Mains Power Supply ............................................................................................ 8
CHAPTER 4
Operation............................................................................................................. 9
4.1 Basic Measurement ............................................................................................. 9
4.2 High Background Noise ..................................................................................... 10
4.3 Intermittent versus Continuous Noise ................................................................ 10
4.4 Voice versus Noise ............................................................................................ 11
4.5 Public Address Sound System Measurement.................................................... 11
4.6 Using an External Signal.................................................................................... 12
CHAPTER 5
Calibration, Certification and Troubleshooting ............................................. 13
5.1 Calibration.......................................................................................................... 13
Calibration Check............................................................................................... 13
Certification ........................................................................................................ 14
5.2 Troubleshooting ................................................................................................. 14
CHAPTER 6
Specifications ................................................................................................... 17

1
Chapter 1
Introduction
Thank you for purchasing Brüel & Kjær’s Echo Speech Source Type 4720. This manual
contains important information for correctly and safely operating Echo Speech Source. Please
take the time to read this manual and familiarise yourself with the advanced features.
1.1 Before First Use
Check for any noticeable damage. Every Brüel & Kjær Echo Speech Source is tested and
inspected before leaving the factory and should arrive in perfect condition. If it has been
damaged in shipment, notify the shipping company immediately. Only the consignee may
institute a claim with the carrier for damage incurred during shipping. Be sure to save the
carton and packing materials for the carrier's inspection.
NOTE: Save the carton and packing material: Always use the original packing materials for
shipping.
For the best results and unit longevity:
• Read the operating and safety instructions applicable to you.
• Keep this manual for future reference.
• Heed all warnings.
• Follow all instructions.
• Do not use this unit near water. Do not spill water or other liquids into or on the unit. Do
not operate the Echo Speech Source while it is wet or immersed in liquid.
• Clean only with a dry cloth.
• Install the unit in accordance with the instructions.
• Do not operate the Echo Speech Source near any heat-producing devices such as radiators,
heat registers or stoves.
• Only use accessories specified by the manufacturer.
• Unplug the apparatus during lightning storms or when not in use for long periods of time.
• Remove batteries when not in use for long periods of time.

Echo Speech Source Type 4270 – User Manual2
• Refer all servicing to qualified service personnel. Servicing is required when the apparatus
has been damaged in any way, such as:
– Liquid has been spilled into the unit
– The unit has been exposed to rain or moisture
– The unit does not operate normally
– The unit has been dropped or the enclosure damaged
• Do not disassemble the unit. There are no serviceable parts inside and disassembly may
void the warranty.
• An experienced user should always supervise this professional audio equipment,
especially if inexperienced adults or minors are using it.

3
Chapter 2
Overview
Echo Speech Source Type 4720 is a small active loudspeaker box that provides calibrated
acoustic signals for speech intelligibility measurements for use with DIRAC Room Acoustics
Software Type 7841.
Echo Speech Source is typically placed at a human speaker position. The received signal at a
listener position is then picked up by a microphone and analysed in DIRAC to arrive at an
accurate qualification of the speech intelligibility through parameters such as Speech
Transmission Index (STI). Echo Speech Source runs on four AA batteries or an external mains
power supply and can be mounted on a standard tripod.
2.1 Control Panel and Loudspeaker
Fig.2.1 Control panel and loudspeaker of Type 4720
1) Raised Level Speaker button (yellow LED): Plays the internal signal through the
loudspeaker (13) at a raised level. The raised level state only applies to the internal MLS
signals (4) and (5), and not to the internal voice signal (6), while in this state the BNC
input (8) is disabled and the BNC output signal (9) is not affected.
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Echo Speech Source Type 4270 – User Manual4
2) Reference Level Speaker button (yellow LED): Plays the internal signal through the
loudspeaker (13) at an A-weighted output level of 60 dB, at a distance of 1 m in front of
the loudspeaker. In this state the BNC input (8) is disabled.
3) Off button (yellow LED): Stops internal signals playing through the loudspeaker (13), and
enables a signal from the BNC input (8) to be played through the loudspeaker. The BNC
output signal (9) is not affected.
4) Continuous Noise button (yellow LED): Selects the internal continuous MLS signal for
the loudspeaker (13) and the BNC output (9).
5) Intermittent Noise button (yellow LED): Selects the internal intermittent MLS signal for
the loudspeaker (13) and the BNC output (9).
6) Test Voice button (yellow LED): Selects the internal test voice signal for the loudspeaker
(13) and the BNC output (9).
7) Input LED (red): Lights up with an overload of the BNC input, and flashes briefly if the
input signal is too low for more than 22 s while the Echo Speech Source is in the Off
state (3) (see also section 4.6).
8) Input Signal BNC socket: External signal input.
9) Output Signal BNC socket: Provides the selected signal type (4), (5) or (6). Not affected
by the loudspeaker level selection buttons (1), (2) or (3). Maximum voltage is
approximately 1.5 Vpeak.
10) External Power Supply socket: Connect a mains power supply with a DC plug accepting a
2.1 mm centre pin (see also section 3.3 and Specifications).
11) Power On/Off button: toggle button.
12) Power On LED (green): illuminated if the power is turned on and briefly blinks if the
demanded power exceeds the available power from the batteries or external power supply.
While blinking, the loudspeaker is muted.
13) Loudspeaker