PD002. Product Data ZIRCON. Loudspeaker-Microphone Probe

Transcription

1 PD002 Product Data ZIRCON Loudspeaker-Microphone Probe Copyright Acoustics Engineering January 2006

2 This page intentionally left blank.

3 Description The Zircon is a loudspeaker-microphone probe for measuring in situ absorption and reflection properties of surfaces. These may be indoor surfaces, such as in concert halls and gyms, or outdoor surfaces, such as road surfaces (ISO , ref [1]), sound barriers installed in a free field (NF S , ref [2]) and traffic noise reducing devices (EN , ref [3]). Using the wall measurement stand, the Zircon can be rotated horizontally and vertically, indicating (and optionally snapping to) each 10 angle. Using the floor measurement stand, the Zircon can be rotated vertically over 360. The Zircon is easy to dismantle and transport in its flight cases. Features Optimal ergonomic design Wall measurement stand 10 angle indication in 2 dimensions (optional snap function) Floor measurement stand enables vertical rotation over 360 Tethered constructions ensure high stability and acoustical transparency Ergonomically placed grips for easy handling High performance miniature microphone Includes protective flight cases Included cables with connectors and lengths of your choice Easy to dismantle and transport Applications ; Measurement of the Sound Power Reflection Factor Q W of road surfaces, using the F-stand. Figure 1. Floor sound absorption and reflection measurement setup. Copyright Acoustics Engineering January

4 ; Measurement of the Reflection Index RI or Sound Insulation Index SI of road traffic noise reducing devices,using the W-stand. ; Measurement of the sound absorption properties of indoor surfaces of large rooms, such as gyms,using the W-stand. Figure 2. Wall sound absorption and reflection measurement setup. 4 January 2006 Copyright Acoustics Engineering

5 Figure 3. Connection to an analyser (not included). The Zircon has to be connected to an analyser, for instance the impulse response measurement program DIRAC by Acoustics Engineering, running on a notebook PC. The analyser has to generate a stimulus, such as an MLS or sweep signal. The received response is a summation of the direct sound from the loudspeaker (incident sound on the surface under test), the sound reflected by the surface under test and unwanted reflections via objects in the neighbourhood. From this response, the analyser has to calculate the overall impulse response by deconvolution (see figure 4). Starting the impulse excitation at t = 0 s, the first sound, coming directly from the loudspeaker, arrives at t = (ds-dm)/c, where ds dm is the source-microphone distance and c is the sound velocity in air. The second instance of the impulse response represents the sound reflected by the surface under test, 2dm/c seconds later, where dm is the distance between microphone and surface under test. Finally, dp/c seconds from the start, the first parasitic reflection arrives at the microphone position, where dp is the distance the wave reflected by the closest object other than the surface under test has to travel from loudspeaker to microphone. Through time-windows, drawn in red in figure 4, the direct and surface-reflected components can be separated from the overall impulse response. Taking into account that for a spherical wave the amplitude is inversely proportional to the distance, the sound reflection and absorption properties of the surface under test can be derived from these components. The lowest significant frequency depends on the length of the time windows. The direct sound time window is right-limited by the start of the surface-reflected sound it has to eliminate, while the surface reflection time window is left-limited by the direct sound tail, and right-limited by the first arriving parasitic reflection it has to eliminate. Both windows can be extended by using the subtraction technique described below [ref 4]. Copyright Acoustics Engineering January

6 c = sound velocity in air [m/s] 0 t direct sound from source (d s-d m) /c 2d m/c sound reflected by surface under test d/c p parasitic reflections from other objects Figure 4. Typical overall impulse response from Zircon sound reflection and absorption measurement. With the subtraction technique, first a free-field measurement is performed by pointing the microphone into a direction with minimum reflections, for instance outdoors into the sky, away from the surface under test. The free-field measurement allows the use of a longer (right extended) direct sound time window, accurately providing the impulse response of the Zircon itself, which represents the direct sound component in figure 4. By subtracting the free-field impulse response from the overall impulse response of figure 4, the direct sound component is removed. Now the surface reflection could arrive earlier (by placing the microphone closer to the surface), and the surface reflection time window can be made longer (left-extended). This longer window extends the usable frequency range. Another advantage of a decreased microphone-surface distance is an increased surface-reflected signal to noise ratio. Components The Zircon Probe comprises the LS14 loudspeaker unit, the CA12 loudspeaker cable assembly, the DPA 4060-B microphone, the MM14 microphone mast, the CA14 microphone cable assembly and the FC14 flight case. The Zircon W-stand, for wall measurements, comprises the WS14 stand with horizontal swivel, the VS14 vertical swivel fork and the FC15 flight case. The Zircon F-stand, for floor measurements, comprises 2 SW12 stand wheel units, the FS14 stand, and the FC16, FC17 and FC18 flight cases. When ordering the Zircon Probe, denote the type of loudspeaker and micophone cable assemblies. For ordering information on a Zircon W-stand with snap function, or a separate component, please contact Acoustics Engineering, 6 January 2006 Copyright Acoustics Engineering

7 Product Data Zircon Probe LS14 loudspeaker unit with a Speakon connector for the loudspeaker and a 3-pole male XLR connector for the microphone. Provides vertical swivel function if used with the VS14 vertical swivel fork. FC14 flight case for the Zircon Probe and its accessories. CA12-xxYYY loudspeaker cable assembly with a Speakon connector for connection to the Zircon loudspeaker. Length and plug at the other side on demand, using the following code in the order number. The default length (omitting xxyyy) is 10 m and the default plug is a 2-pole Speakon connector. xx = length in meters YYY = type of plug YYY = SPK (default 2-p) Speakon connector YYY = XLR (default 4-p) male XLR connector YYY = JCK 6.3 mm jack plug YYY = BAN two 4 mm banana plugs YYY = OPN open ended, no terminator Copyright Acoustics Engineering January

8 Zircon Probe (continued) DPA 4060-B prepolarized omnidirectional miniature condenser microphone from DPA, with microdot connector. MM14 microphone mast, to fixate the microphone position with respect to the loudspeaker. Consists of 6 separable pieces and 3 microphone wire clips. Distance between loudspeaker and microphone 1.00 m (without microphone insert) or 1.25 m (with microphone insert). mast support lower piece middle piece upper piece (with tethers) microphone insert microphone holder wire clips CA14xxYYY microphone cable assembly with 3-pole XLR connector for connection to the Zircon microphone. Length and plug at the other side on demand, using the following code in the order number. The default length (omitting xxyyy) is 10 m and the default plug is a 3-pole XLR connector. xx = length in meters YYY = type of plug YYY = XLR 3-p male XLR connector, balanced YYY = JK3 3.5 mm jack plug, unbalanced YYY = JCK 6.3 mm jack plug, unbalanced 8 January 2006 Copyright Acoustics Engineering

9 Zircon W-stand (for wall measurements) WS14 stand. Enables the source height to be adjusted between 1.5 and 2.2 m. Pinlockable at 1.6, 1.8, 2.0 and 2.2 m. Separate tension wires and carabine hooks provide a stiff construction for the height of 2 m. horizontal swivel, with 10º angle indication, optional snap function, and on top 2 M6 mounting holes at 45 mm distance tension wires FC15 flight case. VS14 vertical swivel fork. Provides a vertical swivel function with 10º angle indication, if combined with the Zircon Probe. Optional snap function. With 2 knurled M6 screws at 45 mm distance, for mounting on the WS14 stand. A counterweight (top right) is used to balance the microphone insert, while a horizontal fixation cord (bottom right) serves as a counterweight in absence of the microphone mast. Alterations reserved Copyright Acoustics Engineering January

10 Zircon F-stand (for floor measurements) FS14 2 tripods with a light-weight tethered bridge, thereby minimizing parasitic sound diffraction and enabling accurate low absorption measurements. Provides a nominal source height of 1.25 m, when placed on two SW12 wheel units. This height can be adjusted. The Zircon is kept in place by a clamp table and forms an integrated part of the construction. FC16 flight case for tubes. FC17 flight case for 2 tripods, clamp table and tension wires. FC18 flight case for 2 SW12 stand wheel units. Alterations reserved 10 January 2006 Copyright Acoustics Engineering

11 Characteristics The Zircon is compliant with the ISO [ref 1], the NF S [ref 2] and the CEN/TS [ref 3] standards. Figure 5 shows the free-field impulse response. 100% 50% 0% -50% -100% t [ms] Figure 5. Zircon impulse response, measured with microphone mast attached and source-microphone distance of 1.00 m. Zircon Probe Parameter Condition Min Typ Max Unit LS14 loudspeaker unit Operating frequency range Third octave frequency bands Hz Nominal impedance 8 L Power handling Sound Pressure Level Continuous Peak At 1 m distance in front, at 50 W applied power W W 104 db Microphone power supply PP3 battery 9 V Power supply operation time Starting from full battery 140 h Connectors Microphone input Microphone output Loudspeaker input Microdot 3-pole XLR Speakon Weight 9.5 kg DPA 4060-B microphone Diameter Prepolarized condenser element 5.4 mm Operating frequency range -3 db Hz Sensitivity At 1 khz mv/pa Equivalent noise level CCIR db Copyright Acoustics Engineering January

12 Zircon Probe (continued) Parameter Condition Min Typ Max Unit MM14 microphone mast Source-microphone distance Without microphone insert With microphone insert Weight Including microphone insert 0.9 kg FC14 flight case Dimensions 45 x 45 x 45 cm Weight Filled 20 kg m m Alterations reserved Zircon W-stand (for wall measurements) Parameter Note Min Typ Max Unit WS14 stand Horizontal angle of rotation Provided Zircon height 10º angle indication Optional snap function Rotational centre Lockable at 1.6, 1.8, 2.0, 2.2 m Tensable at 2 m unlimited deg m Weight Without snap function 4.5 kg VS14 vertical swivel Vertical angle of rotation LS14 loudspeaker unit 10º angle indication Optional snap function deg Mounting screw distance 2 knurled M6 screws 45 mm Bottom plate width 40 mm Weight Without snap function 2.5 kg FC15 flight case Dimensions 123 x 35 x 17 cm Weight Filled 16.5 kg Alterations reserved 12 January 2006 Copyright Acoustics Engineering

13 Zircon F-stand (for floor measurements) Parameter Condition Min Typ Max Unit SW12 stand wheel units Provided additional stand height 13 cm Dimensions Each unit, folded, L x W x H 69 x 35 x 20 cm Weight Each unit 8.5 kg FS14 stand Provided source height Including SW12 units 1.25 m Flight cases Dimensions L x W x H Weight FC16 (tubes) FC17 (tripods, table, wires) FC18 (stand wheel units) FC16, filled FC17, filled FC18, filled 110 x 17 x x 37 x 22 cm 73 x 39 x kg 30 Alterations reserved References [ref 1] ISO :2002 Acoustics Measurement of sound absorption properties of road surfaces in situ Part 1: Extended surface method. [ref 2] [ref 3] [ref 4] [ref 5] NF S Acoustique Code d essai pour la détermination de caracteréstiques intrinsèques des écrans installés in situ. CEN/TS :2003 Road traffic noise reducing devices Test method for determining the acoustic performance Part 5: Intrinsic characteristics In situ values of sound reflection and airborne sound insulation. Mommertz E., Angle-dependent in-situ measurements of reflection coefficients using a subtraction technique. Applied Acoustics, 46, 1995, pp Adrienne Research Team, Test methods for the acoustic performance of road traffic noise reducing devices Final report - European Commission DGXII SMT Project MAT1-CT94049, 1998 Copyright Acoustics Engineering January

14 Acoustics Engineering develops systems for the prediction and measurement of acoustical parameters, resulting in user-friendly tools that enable you to perform fast and accurate acoustical measurements and calculations. For information on our products, please contact Acoustics Engineering Phone/Fax: Mail: Website: Acoustics Engineering Groenling MZ Boxmeer The Netherlands Copyright Acoustics Engineering 2006 All rights reserved. No part of this document may be reproduced or transmitted in any form or by any means, electronical or mechanical, without the prior written permission of Acoustics Engineering.