SSE Audio SSE Audio - SSE Audio Group

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

OC

PR

MM

01

OC

DB

MM

Date: April 2014 Status: FINAL Issued To: SSE Audio Issue Notes: Added Introduction Change Status to Final. Added measurement and

02

MM

DB

MM Normalisation info

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


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

VC-101612-EN-RP-0001 Page | 3


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

VC-101612-EN-RP-0001 Page | 4


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).

VC-101612-EN-RP-0001 Page | 5


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

VC-101612-EN-RP-0001 Page | 6


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


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

VC-101612-EN-RP-0001 Page | 7


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


105 96.7 89.5 70.6 63.5 59.1

Range, dB

4.3 5.3 4.1 5.0 4.4


105 95.3 89.4 70.0 63.1 59.8

Range, dB

2.1 2.7 3.4 2.4 2.1

VC-101612-EN-RP-0001 Page | 8


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


105 95.3 90.8 70.9 64.1 60.3

Range, dB

8.5 3.8 3.7 3.4 2.5


105 95.7 91.2 71.4 64.6 60.9

Range, dB

4.3 5.3 4.5 4.5 4.8

VC-101612-EN-RP-0001 Page | 9


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


105 91.7 88.8 80.0 71.8 66.2

Range, dB

3.7 4.2 4.8 5.2 3.0


105 90.9 87.0 79.0 71.5 66.5

Range, dB

2.2 3.2 5.7 3.9 4.2

VC-101612-EN-RP-0001 Page | 10


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


Range, dB

80.3 74.5 68.7

5.8 2.7 5.1

105


Range, dB

79.7 73.8 69.9

3.1 2.5 3.2

105

VC-101612-EN-RP-0001 Page | 11


2.7

Pink Noise – Rear of stage

Measurement Meter

Distance (m)


XL2-03 XL2-06 XL2-05

50 100 150

78.9 75.5 72.8

Range, dB


Range, dB

1.5 1.9 2.9

80.1 76.5 73.7

1.5 1.2 2.2

VC-101612-EN-RP-0001 Page | 12


2.8

Music – Rear of stage

Measurement Meter

Distance (m)


XL2-03 XL2-06 XL2-05

50 100 150

79.0 76.9 74.8

Range, dB


Range, dB

2.0 1.1 2.6

83.2 80.4 77.6

2.0 1.7 2.6

VC-101612-EN-RP-0001 Page | 13