FAQ

Regulations and standards

	Environment	Personnel protection	Workplaces
ICPE (general case)	Arrêté du 23/01/1997 Inspection every 3 years Compliance with LP value + emergence (overall) Measurements outside dwellings Minimum threshold: 35 dBA	Noise Decree 2006-892 of 19/07/2006 80 dBA / 135 dBC (inf.) 85 dBA / 137 dBC (sup.) 87 dBA / 140 dBC (limit with PPE) Compte professionnel de prévention 81 dBA – 600 h/year 135 dBC – 120 times/year Vibrations Decree 2005-746 of 04/07/2005 0.5 m/s² (body) – 2.5 m/s² (hand-arm) 1.15 m/s² (body) – 5 m/s² (hand-arm)
Non-ICPE industries	Decree of 31/08/2006 Initial inspection Compliance with overall + spectral emergence Indoor / outdoor measurements Minimum threshold: 30 dBA (outdoor) / 25 dBA (indoor)		Arrêté du 30/08/1990 Minimum sound reduction depending on surface area (if potential exposure > 85 dBA)
Electrical substations	Arrêté du 26/01/2007 Non-systematic control Compliance with overall residential emergence Minimum threshold: 30 dBA
Measurements	NFS 31-010	NF EN ISO 9612 – 2025 (noise) NF EN 14523 A1 (body vibrations) NF EN 5349-1 and 5349-2 (hand-arm)Noise

How do decibels add up?

Noise levels are most commonly expressed in decibels (dB), a logarithmic unit. It is therefore not possible to “classically” add up these values.

Tool for adding decibles

How to calculate the distance effect?

Distance has a significant impact on measured noise levels. The further away from the source, the lower the noise level measured.

Distance effect calculation tool

How do you calculate an overall sound level from a spectrum?

With the exception of pure sound, which is made up of a single frequency (for example, the sound emitted by your telephone before dialing), noise is made up of a superposition of multiple frequencies.

The sound spectrum is used to characterize noise more precisely. By analyzing a spectrum, it is possible to obtain the noise’s “identity card”. This makes it possible to propose solutions adapted to each spectrum.

The tool below calculates the overall level of a sound spectrum by logarithmically summing each octave band. The overall level is expressed both unweighted (dB Lin) and A-weighted (db(A)).

Tool for calculating sound level from a spectrum

1. What are the differences between the DA1, DA2 & DA3 design approaches in API 618?

DA1: It is requested that the anti-pulsation balloon be designed using analytical techniques in order to satisfy the permissible in-line pulsation levels and pressure drops.

However, SIM Engineering still designs its anti-pulsation balloons using acoustic simulation rather than an analytical method.

DA2: An acoustic simulation of the compressor, anti-pulsation balloons, and customer piping lines is requested. A review of the support system is requested, but only based on an analytical method and experience.

DA3: As for DA2, an acoustic simulation is required. In addition, a mechanical response study is required using modal analysis software.

2. Are the vibrations caused by the reciprocating compressor or by pulsation?

Vibrations directly induced by the reciprocating compressor are typically..:

• Periodic forces generated by unbalanced moving masses.
• Periodic torque generated by cylinder offset.
• Vertical forces at the stock guide.
• Cylinder elongation due to internal compression forces.
• Particularly for high-speed compressors, misalignment of rotating parts.

Pulsation-induced vibrations are typical:

• Unbalanced forces induced by pulsations through volumes.
• Pulsation-induced unbalanced forces on pipe sections between bends and closed ends.
• The effect of pulsations on the PV diagram and compressor vibrations.

3. I thought a screw compressor was free of pulsation and vibration?

A screw compressor (dry or wet) does not compress the gas continuously, but in a series of flow bursts cadenced by the number of screw lobes m2le. Pulsations are greater on the discharge side than on the suction side, particularly when the compressor is operating in Over- or Under-Compression (meaning that the maximum internal pressure reached inside the screw is higher or lower, respectively, than the process discharge pressure).

1 What is monitoring?

Monitoring is a service providing a modular station for acoustic and/or vibration measurements. It is our preferred tool for assignments requiring long-term monitoring.

2 In which sector is it recommended?

Noise pollution has become a key issue in all sectors of activity. Our stations are used not only in the construction industry for site monitoring, but also in industry, cities and the environment…

3 How is follow-up carried out?

SIM Engineering has developed an online monitoring platform that enables you to view the progress of acoustic and/or vibration measurements in real time, as well as the history of measurements, count the number of noise or vibration exceedances, listen to automatic or manual audio triggers, and edit monthly and/or weekly reports.

4.is the monitor connected?

Our stations are connected and use the 4G network to communicate with the online monitoring platform and to send SMS/Mail alerts to the people in charge of monitoring when predefined values are exceeded.

5 What’s new?

Thanks to their productivity, our monitoring stations are constantly evolving. Combining monitoring of pollution emissions with noise and vibration emissions in the near future.