Apr 2, 2014 - Head Office: 21 Station Road West, Oxted, Surrey, RH8 9EE. Tel: + 44 ... The two line array systems were p
SSE Audio Hatfield Measurements Results VC-101612-EN-RP-0001 Rev 02 April 2014
SSE Audio Hatfield Measurements Initial Results April 2014
Contents 1
Introduction ...................................................................................................................................... 3
2
Initial Results ................................................................................................................................... 6
Vanguardia Consulting Document Control Document Title: Hatfield Measurements Initial Results Project Number: VC/101612 Document Reference: VC-101612-EN-RP-0001-R00 Revision: Prepared By: Checked: Passed: Revision: 00
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Date: April 2014 Status: FINAL Issued To: SSE Audio Issue Notes: Added Introduction Change Status to Final. Added measurement and
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Professional Associations: Vanguardia Consulting London Office: Southbank Technopark, 90 London Road, London, SE1 6LN Head Office: 21 Station Road West, Oxted, Surrey, RH8 9EE
Tel: + 44 (0) 207 922 8861 Fax: + 44 (0) 8700 516 196
Institute of Acoustics The Association of Noise Consultants The Audio Engineering Society Institute of Engineering and Technology
SSE Audio Hatfield Measurements Initial Results April 2014
1 Introduction 1.1
Vanguardia
Consulting
has
been
appointed
by
SSE
Audio
group
to
undertake
a
set
of
acoustic measurements pertaining to the propagation of sound from two large format line array loudspeaker systems.
1.2
The purpose of the acoustic measurements is to compare the far field propagation of sound from the arrays at distances that are typically outside of the audience area.
1.3
The two line array systems were provided for the test by two different manufacturers, these were;
L’Acoustics K1
Martin Audio MLA
1.4
Each system comprised a single flown array with a trim height of 12.5m and an array length of approximately 5.25m. Due to the physical size of the loudspeaker units there were slightly different
quantities
of
units
in
each
array,
these
were
12
K1
units
and
14
MLA
units.
Subwoofer loudspeakers were used for listening tests only and not part of the measurement exercise.
Figure 1 – K1 and MLA arrays
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SSE Audio Hatfield Measurements Initial Results April 2014
1.5
The arrays were configured to cover an audience distance at standing head height from 10m to 110m horizontally on-axis to the arrays. The arrays were set to provide a 6dB reduction in level from the front to the rear of the on-axis coverage distance. Array configurations, both physical and control settings were implemented by representatives from the manufacturers.
1.6
The
two
arrays
were
hung
9.4
metres
apart
(as
close
as
practically
possible
with
the
constraints of the tower structures) and the reference on-axis line was set midway between the two arrays.
1.7
The on-axis frequency response of the two arrays was normalised by SSE engineers to provide a nominally similar frequency response at 60m on-axis.
1.8
The measurements were undertaken at Hatfield Country Park. The arrays were installed such that
they
were
facing
due
east.
This
configuration
allowed
a
number
of
measurement
positions up to 820m from the arrays and up to 60 degrees off-axis as well as at the rear of the arrays.
1.9
The measurement locations are shown on the site plan in the Appendix.
1.10
On the day of the measurements the following weather conditions were measured on the site.
Date
Time
25-Mar 25-Mar 25-Mar 25-Mar 25-Mar 25-Mar 25-Mar 25-Mar 25-Mar 25-Mar 25-Mar 25-Mar 25-Mar 25-Mar 25-Mar
11:00 11:20 11:40 12:00 12:20 12:40 13:00 13:20 13:40 14:00 14:20 14:40 15:00 15:20 15:40
Temperature, degrees C 8.5 7.7 8.7 9.4 10.5 8.6 8.9 9.6 9.7 9.6 9.4 9.6 8.7 10 10.1
Wind speed, km/h 6.3 6.6 6.9 8.7 9.7 9.5 9.5 8.2 7.4 10 9.7 7.9 8.7 6.1 7.7
Wind Direction, Degrees 67.7 90 67.5 112.5 90 90 67.5 67.5 67.5 112.5 67.5 90 135 135 45
% relative humidity 74 74 70 67 63 67 67 63 61 62 63 60 64 62 59
TABLE 1 – Weather Measurements at 60m on-axis
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SSE Audio Hatfield Measurements Initial Results April 2014
1.11
During the measurements between midday and 4pm the wind was consistently blowing from the easterly direction with a speed of approximately 6-8 km/h. This weather condition was reasonably
stable
throughout
all
the
measurements.
This
places
all
of
the
on-axis
measurements upwind from the arrays. In this condition the standard theoretical models of acoustic propagation are not accurate and measured levels tend to be between 5-20 dB lower than mathematical predictions based on neutral weather conditions (as detailed in Predicting Outdoor Sound, Taylor & Francis by Keith Attenborough, Page 13)
1.12
Acoustic
measurements
are
not
stable
when
measured
upwind
and
small
variations
in
meteorological conditions can cause significant changes in the propagation of sound and resulting sound pressure levels.
1.13
Source for measurements was pink noise and music provided by SSE (Slipknot).
1.14
Simultaneous broadband and A-weighted sound levels were measured at each location at a microphone height of 1.5m above ground.
1.15
Measurements taken were Leq (equivalent average) over a time period of 10 seconds. A number of contiguous measurements were taken in each period (typically 6) and several periods were taken at each location (typically 3).
1.16
The raw data has been post-processed to normalise for the level at the agreed reference location. The reference location was within the coverage area of the arrays and at 50m distance on-axis to them. The normalisation level used was 105 dB(A).
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SSE Audio Hatfield Measurements Initial Results April 2014
2 Initial Results 2.1
Pink Noise – On Axis
Measurement Meter
Distance (m)
XL2-10 XL2-07 XL2-03 XL2-06 XL2-04 XL2-02 XL2-08 XL2-01
50 150 200 300 500 600 700 820
Normalised K1 LAeq, dB(A) dB(A)
105 97.3 89.6 84.6 68.3 64.9 61.9 53.3
Range, dB
4.9 4.8 6.0 5.3 3.5 4.8 3.4
Normalised Normalised MLA LAeq, dB(A) dB(A)
105 97.4 90.6 86.0 68.8 63.9 60.7 52.2
Range, dB
4.9 5.0 5.6 3.7 4.3 4.8 4.8
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SSE Audio Hatfield Measurements Initial Results April 2014
2.2
Music – On Axis
Measurement Meter
Distance (m)
XL2-10 XL2-07 XL2-04 XL2-02 XL2-08 XL2-01
50 150 200 300 500 600 700 820
Normalised K1 LAeq, dB(A) dB(A)
105 98.4 70.4 66.6 64.0 55.8
Range, dB
5.4 2.8 2.3 5.1 2.4
Normalised MLA LAeq, dB(A) dB(A)
105 97.6 69.9 66.4 62.8 54.3
Range, dB
5.1 1.7 2.1 3.3 2.9
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SSE Audio Hatfield Measurements Initial Results April 2014
2.3
Pink Noise – 30 degrees off axis
Measurement Meter
Distance (m)
XL2-10 XL2-07 XL2-06 XL2-08 XL2-02 XL2-01
50 150 200 400 500 600
Normalised K1 LAeq, dB(A) dB(A)
105 96.7 89.5 70.6 63.5 59.1
Range, dB
4.3 5.3 4.1 5.0 4.4
Normalised MLA LAeq, dB(A) dB(A)
105 95.3 89.4 70.0 63.1 59.8
Range, dB
2.1 2.7 3.4 2.4 2.1
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SSE Audio Hatfield Measurements Initial Results April 2014
2.4
Music – 30 degrees off axis
Measurement Meter
Distance (m)
XL2-10 XL2-07 XL2-06 XL2-08 XL2-02 XL2-01
50 150 200 400 500 600
Normalised K1 LAeq, dB(A) dB(A)
105 95.3 90.8 70.9 64.1 60.3
Range, dB
8.5 3.8 3.7 3.4 2.5
Normalised MLA LAeq, dB(A) dB(A)
105 95.7 91.2 71.4 64.6 60.9
Range, dB
4.3 5.3 4.5 4.5 4.8
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SSE Audio Hatfield Measurements Initial Results April 2014
2.5
Pink Noise – 60 degrees off axis
Measurement Measurement Meter
Distance (m)
XL2-10 XL2-07 XL2-05 XL2-05 XL2-03 XL2-04
50 150 200 300 400 500
Normalised K1 LAeq, dB(A) dB(A)
105 91.7 88.8 80.0 71.8 66.2
Range, dB
3.7 4.2 4.8 5.2 3.0
Normalised MLA LAeq, dB(A) dB(A)
105 90.9 87.0 79.0 71.5 66.5
Range, dB
2.2 3.2 5.7 3.9 4.2
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SSE Audio Hatfield Measurements Initial Results April 2014
2.6
Music – 60 degrees off axis
Measurement Meter
XL2-10 XL2-05 XL2-03 XL2-04
Distance (m)
50 150 200 300 400 500
Normalised K1 LAeq, dB(A) dB(A)
Range, dB
80.3 74.5 68.7
5.8 2.7 5.1
105
Normalised MLA LAeq, dB(A) dB(A)
Range, dB
79.7 73.8 69.9
3.1 2.5 3.2
105
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SSE Audio Hatfield Measurements Initial Results April 2014
2.7
Pink Noise – Rear of stage
Measurement Meter
Distance (m)
Normalised K1 LAeq, dB(A) dB(A)
XL2-03 XL2-06 XL2-05
50 100 150
78.9 75.5 72.8
Range, dB
Normalised MLA LAeq, dB(A) dB(A)
Range, dB
1.5 1.9 2.9
80.1 76.5 73.7
1.5 1.2 2.2
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SSE Audio Hatfield Measurements Initial Results April 2014
2.8
Music – Rear of stage
Measurement Meter
Distance (m)
Normalised K1 LAeq, dB(A) dB(A)
XL2-03 XL2-06 XL2-05
50 100 150
79.0 76.9 74.8
Range, dB
Normalised MLA LAeq, dB(A) dB(A)
Range, dB
2.0 1.1 2.6
83.2 80.4 77.6
2.0 1.7 2.6
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