TESTBODY – INFO

Test and certification body printing and paper converting, 65173 Wiesbaden

Tel. (+49 6 11) 1 31-82 19, Fax (+49 6 11) 1 31-81 55, email: pruefstelle-dp@bgetem.de, www.bgetem.de/pruefstelle-dp

Issue: 2007/09 Order Nr. 917e

Determination of emission sound pressure levels of printing and paper converting machines 1. Noise emission determination required by law Information on noise emission is an important part of instruction handbooks and technical docu-mentation and is regulated by law. As stipulated in the Machinery Directive 98/37/EC, machine manufacturers are required to de-clare obliging and reproducible noise emission values for their specific machine(s). The two main parameters are: the emission sound pressure level at the workstation Lp [dB(A)] the sound power level Lw [dB(A)] To determine these values, various basic measuring standards have been developed within the framework of European standard harmonisation and also the standard EN 13023 "Noise meas-urement methods for printing, paper converting, paper making machines and auxiliary equipment - Accuracy grades 2 and 3" specifying machine-specific noise test codes. 2. Noise test codes 2.1 Measuring points and operating conditions The measuring points required for determining the emission sound pressure levels of specific machines at workstations and other specified positions and the operating conditions are defined in the normative annexes A to J of standard EN 13023. For all machines within the scope of EN 13023 which are not listed in the annexes A to J, meas-urements must be taken under possible typical operating conditions with the machine running at a speed of 100 % of the maximum machine speed specified by the manufacturer. As measuring points, typical workstations must be selected. 2.2 Measuring of emission sound pressure levels In order to select the standard applicable for the determination of emission sound pressure levels of a specific machine, EN ISO 11200 "Noise emitted by machinery and equipment - Guide-lines for the use of basic standards for the determination of emission sound pressure levels at a workstation and other specified positions" must be applied. As measurements are taken in the room where they are installed under operational conditions and the preferred degree of accuracy is 2, measuring is done in accordance with EN ISO 11204 "Noise emitted by ma-chinery and equipment - Measurement of emission sound pressure levels at the workstation and other specified position - Method requiring environmental corrections".

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3. Measuring procedures / Determination of basic values 3.1 Measuring equipment For measuring, integrating sound level meters must be used that accord to IEC 804. Where sound pressure level fluctuations can be verified as insignificant, a conventional sound level me-ter according to IEC 651 may be used. Meters including their auxiliary equipment must comply to the requirements of class 1 (error limit ± 0,7 dB). Before and after each series of measurements, the measuring devices must be calibrated. Sound level calibrators must comply to class 1 of IEC 942. Regular testing of the entire measuring equipment is required at intervals of at least two years. The date of the most recent test with re-sults complying with the requirements of IEC standards must be recorded. 3.2 Microphone positions The position of microphones is to be determined in accordance with the machine-specific noise test code EN 13023. Where no stipulations are made, microphones must, for seated positions, be placed at (0,80±0,05 m) above the centre of the seat. For standing operating positions, the microphone height is (1,550±0,075 m) above foot level unless a specific noise test code exists. The microphone positions selected must be described in the test report. 3.3 Values to be measured 3.3.1 The following values must be measured at each position selected and for the oper-

ating periods or the operating cycles selected for the machine under test: 1. The time-averaged A-weighted emission sound pressure level L´pA (with the inverted

comma identifying the values as measured with the machine running) according to the stipulations of EN 13023;

2. The background noise sound pressure level L´´pA with the machine OFF.

Note: The duration of measuring must be at least 15 s for each measuring point.

3.3.2 The following measurements must be made to determine the environmental influ-

ences on each of the measuring points selected for the machine under test:

1. The mean surface sound pressure level 'L in accordance with item 3.4.1.1 (clause 4 and/or note 1);

2. Determination of environmental influences also requires measuring the reverberation

time TN. Reverberation is the period of time following an isolated single sound event, for example a shot from a starting pistol, during which the sound pressure level is re-duced by at least 60 dB, provided that the sound intensity of the source noise is at least 60 dB above the basic level. For sound levels of below 60 dB, the sound level diagram is extrapolated accordingly or the time T/2 is determined during which the levels is reduced by 30 dB.

For small-scale measurements, the following points must be considered: Measuring points should cover the entire measuring area as appropriate. Individual microphones should be positioned at a distance of at least about two metres. Normally, three or four microphone positions are considered adequate.

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3.4 Values to be determined The following terms and definitions are taken from the respective standards:

Background noise correction K1 : A frequency-dependent correction value in decibel to take account of influences from background noises (radiated for example from other machines in the room or by ventila-tion equipment) on the emission sound pressure levels at the measuring points specified for the machine. Where A-weighting is applied, K1A is determined from the A-weighted measuring values. (For calculation see 3.4.1.2). Environmental indicator K2 : This value is used to take account of the influence of sound reflected from or absorbed by the surfaces limiting the room (floor, ceiling, walls) on the surface sound pressure level. K2 (or K2A if A-weighted) is frequency dependent and is stated in decibel. (For calculation see 3.4.1.3).

Local environmental correction K3 : Takes account of the influence of reflected and absorbed sound on the emission sound pressure level at the points specified for the machine. K3 (or K3A if A-weighted) depends on frequency as well as position and is stated in decibel. The value of K3A determines the grade of accuracy achieved for measurements carried out in accordance with EN ISO 11204:

K3A ≤ 2 dB (Grade 2 accuracy) K3A ≤ 7 dB (Grade 3 accuracy)

(For calculation see 3.4.1.1) 3.4.1. Emission sound pressure level In order to determine the emission sound pressure level for a specified position j, background noise correction K1 and local environmental correction K3 must be applied on the sound pressure level measured. The calculation is:

jAjApjApjA KKLL 31'

L pjA: corrected, A-weighted emission sound pressure level at position j L' pjA: measured, A-weighted emission sound pressure level at position j

3.4.1.1 The local environmental correction K3 In order to determine correction K3, the sound pressure levels must be measured on a measuring plane covering the entire surface of the machine. This is required as the sound levels measured at specific measuring points are influenced by the total sound emission of the machine. One method for determining the local environmental correction K3 is using the equivalent sound absorption area A of the measurement room. K3A is calculated as follows:

dBSA

K pjALLj

)''(1,0

3 1041

11lg10

S: area of measurement surface in m2, for which 'L is determined A: equivalent sound absorption area of the measurement room in m2

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The equivalent sound absorption area A of the measurement room is determined by applying the Sabine equation for calculating the reverberation time. A in m2 is calculated as follows:

NT

VA 16,0

V: volume of measurement room in m3 TN: reverberation time of measurement room in s

The mean value of the (uncorrected) sound pressure level 'L on a measuring surface area S at a given distance d from the machine is calculated as follows:

dBN

LN

i

iL

1

'1,0101

lg10'

where 'L is the mean value of the sound pressure levels L’i measured at N points around the machine under test. It is recommended, but not mandatory that the arrangement of microphone positions is identical to that used for determining the sound power levels according to the envel-oping measurement surface method defined in EN ISO 3744 "Determination of sound power le-vels of noise sources - Engineering method employing an enveloping measurement surface over a reflecting plane (grade 2 accuracy)". The procedure is described below. 3.4.1.1.1 Determining the enveloping measurement surface Step one in this procedure is important for sound emission determination, but its application needs some experience. To start with, a hypothetical rectangular parallelepiped reference box is determined which closely fits the shape of the machine and includes all parts of the equipment deemed to emit noise. Starting from this hypothetical reference box, a parallelepiped enveloping measurement surface is defined with a preferred distance d of 0,5 m or 1 m from the box. This measurement surface extends down to the floor and may reach close walls. The measurement surface area S is calculated, for example for a stand-alone machine, as fol-lows:

)(4 cabcabS and:

dLc

dLb

dLa

3

2

1

5,0

5,0

(L1, L2 and L3: length, width, height of the reference box (machine); d: measuring distance) 3.4.1.1.2 Determining the measuring points on the measurement surface Each plane of the measurement surface is considered on its own and is subdivided into rectan-gular partial areas of identical size with a maximum side length equalling 3d. Microphone posi-tions are located in the middle and at each corner of each partial area. The arrangement of mi-crophones on a partial area could, for example, be as follows:

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3.4.1.1.3 Notes Note 1:

The application of relevant frame standards for the determination of the local environ-mental correction K3 has appeared to be problematic in practice, especially when applied to large machines. The conditions defined in these standards are often impossible to achieve or they can be complied with only at unacceptable expense. As can be derived from the example above, quite a considerable number of microphone positions would be required for large machines: A total of five possible planes would have to be covered with microphone positions like this, including the top plane, the two sides, the front and the rear of the machine. In order to reduce the extent of measuring to a minimum, a simplified method may be used, provided that the noise radiated from the machine is constant for a given time. For determining the mean sound pressure level on the measuring surface 'L , discrete adja-cent measuring points can be combined to make a measurement path at a distance d from the reference box. The microphone is then conducted in a continuous movement at constant speed along the measurement paths of the measurement surface. Results are integrated continuously so that mean values can be derived immediately.

Example: Measuring point arrangement according to EN ISO 3744 for relatively

small machines with a minimum of 9 measuring points for grade 2 accu-racy

Note 2:

Another problem occurring with EN ISO 11204 is that in the event of a minimum sound level at the workstation the argument of the logarithm function in the equation for deter-mining the local environmental correction K3j tends to become negative, thus preventing a solution by way of calculation. This problem can be solved by applying a two-step method for calculating the environ-mental correction: In the first step, argument Z of the logarithm function is calculated. If the result is an ar-gument less than the value Zlimit with K3 equalling 7 dB, then this minimum value Zlimit is used in the second step to calculate K3.

However, this method results in calculated emission sound pressure levels becoming less accurate to the same degree as the "real" environmental influence exceeds the value of 7 dB. For environmental corrections of 7 dB and resulting emission sound pressure levels of X dB, the declaration should be: "Emission sound pressure level Lp ≤ dB(A), grade 3 accuracy"

measuring path 3

d

1

2

3

4

56

7 8

9

measuring path 1

measuring path 2

reference box

reflecting plane d

d

= measuring points

6

The equation provided in EN ISO 11204 is therefore modified as follows:

)''(1,010

41

11 pjALL

S

AZ

and:

1für0K

12,0für)lg(10K

0,2für7K

3j

3j

3j

Z

ZZ

Z

Note 3: Environmental corrections are not allowed where measuring points are placed inside cab-ins (for example control stations).

3.4.1.2 Criterion for background noise correction K1 Background noise corrections are determined on the basis of the following equation:

dBK Lj )101lg(10 1,0

1

where ∆L is the difference between sound pressure levels measured at a predefined position with the machine running L’pjA and with the machine switched off L’’pjA. Restrictions according to EN 11204: ∆L > 10 dB: K1 can be defined as 0 ∆L < 6 dB: i.e. K1>1,3 dB and measurement is invalid according this standard 3.4.1.3 Test environment An important criterion for measuring emission sound pressure levels at workstations and other defined positions is the test environment which may have a considerable influence on the meas-urement results. This is identified by the environmental indicator K2 which specifies the degree the test environ-ment deviates from ideal free field conditions. The value of K2 may be 7 dB maximum. K2 is cal-culated as follows (see for example annex A of EN ISO 3744):

dBASK )]/(41lg[102

3.4.2 Sound power levels The sound power level is determined on the basis of EN ISO 3744 and EN ISO 3746 which di-rectly relate to EN ISO 11204. Based on the values determined, the following equation is used for calculating the sound power level:

021w

S

S10lgKKL'L ; S0 = 1 m2

4. Test report The test report on the noise measurements carried out must give all information allowing verifica-tion of test results under practically equal measuring conditions. Test reports should also include photos or drawings of the measuring points. Information must include all technical details required by the noise test code (installation and operating conditions). Deviations from the relevant standards must be clearly identified. It is also required to name the machine manufacturer and list all relevant machine data and the time and place of the test as well as the person in charge.

1st working sheet

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1. Describing measuring conditions Machine

Designation:

Type: Year of manufacture: Serial No.

Dimensions (length x width x height): m x m x m Operating condition

Production speed (80% of nominal speed):

Material (format, quality, type of feeding etc.):

Measuring surface and measuring point:

Distance d from reference box: m

Machine layout with measuring points:

2nd working sheet

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2. Measuring machine noise and background noise correction K1 A-weighted sound pressure level:

Nr. Measuring point

(described according to EN13023) sound pressure

level L’pA [dB]

background noise level

L’’pA [dB] 1

2

3

4

5

6

7

8

Background noise correction: dBK Lj )101lg(10 1,0

1

Measuring point

no. „j“

background noise distance ∆L = L’pA - L’’pA [dB]

background noise correction K1 [dB]

1

2

3

4

5

6

7

8

Check: K1j ≤ 1,3 dB

3rd working sheet

9

3. Verifying the environmental indicator K2 Room parameters

Dimensions (length x width x height): m x m x m

Room volume V: m3 Reverberation time TN: s

Equivalent sound absorption area A:

NT

VA 16,0 = m2

Measuring surface area S for measuring distance d from reference box:

a. stand-alone: S = 4(ab + bc + ca) = m2 a = 0,5 L1 + d = m b = 0,5 L2 + d = m

c = L3 + d = m

a. 3 free sides: S = 2(ab + bc + ca) = m2 a = 0,5 L1 + d = m b = L2 + d = m

c = L3 + d = m

a. 2 free sides: S = ab + bc + ca = m2 a = L1 + d = m b = L2 + d = m

c = L3 + d = m

Environmental indicator K2:

)]/(41lg[102 ASK = dB

Check: K2 ≤ 7 dB

4th working sheet

10

4. Local environmental correction K3

Mean, uncorrected sound pressure level 'L on any measuring surface area S:

N

i

iL

NL

1

'1,0101

lg10' = dB

Local environmental correction:

dBSA

K pjALLj

)''(1,0

3 1041

11lg10

where

)''(1,010

41

11 pjALL

S

AZ

and K3j = 7 for Z ≤ 0,2 K3j = -10 lg (Z) for 0,2< Z ≤ 1 K3j = 0 for Z > 1

Measuring point no.

„j“ Z

[dB] local environmental correction

K3 [dB] 1

2

3

4

5

6

7

8

5th working sheet

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5. Determining the emission sound pressure level LpA

jAjApjApjA KKLL 31' J Sound pressure

level L’pA [dB]

background noise correc-tion

K1 [dB]

local environmental

correction K3 [dB]

emission sound pressure level

LpA [dB]

1

2

3

4

5

6

7

8

Test report

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Manufacturer:

(Address)

Date of test:

Test carried out by:

Place of test:

Machine data:

Description:

Type:

Year of manufacture:

Machine number:

Technical data: Machine dimensions (length x width x height):

maximum speed:

Noise reduction measures: (for example description of enclosures provided)

Remarks: (space left for describing any installation and operating conditions which are not specified in the normative annexes)

Measuring conditions:

Measuring in accordance with noise test code: (EN number with normative annex - grade of accuracy) for example EN 13023 H2.2 – grade 2

Machine speed: (generally 80 % of maximum speed)

Material format:

Material quality:

Remarks: (space left for, for example, description of the method of material feeding, devia-tions from the noise test code etc.)

Room specification:

Room dimensions (length x width x height) or volume V:

Room reverberation time:

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Test results:

Description of measuring points: L’pA [dB]

L’’pA [dB]

K1A [dB]

K2A [dB]

K3A [dB]

Grade

LpA [dB]

1.

2.

3.

4.

5.

Legend: L’pA: time mean value of machine sound pressure level L’’pA: time mean value of the background sound pressure level K1: background noise correction LpA: emission sound pressure level at the work-

station K2: environmental correction acc. to EN ISO 11204 LpA = L’pA - K1A - K3A K3: local environmental correction Grade: grade of accuracy

The following standards were applied: EN 13023 Noise measurement methods for printing, paper converting and

paper making machines and auxiliary equipment - Grade of accu-racy 2 and 3: 10/2003

EN ISO 11204 Acoustics - Noise emitted by machinery and equipment - Meas-urement of emission sound pressure levels at the work station and at other specified positions - Method requiring environmental corrections: 6/1996

Measuring devices used: Measuring device: (type, designation, manufacturer, serial number)