ISO 14509 Noise Testing

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The amended Recreational Craft Directive, in particular Post Construction Assessment (PCA), which was adopted in the UK on January 1st 2006, requires power craft of 24m or less to demonstrate that their noise levels are below prescribed limits. 

For slower (displacement) craft we can do this simply by calculation and do not need any physical testing. 

In theory, craft fitted with drive systems which have integral exhausts, such as outboards and stern drives should be covered by tests undertaken by the engine manufacturer.  However, this will only be the case if they (the manufacturer) intended the drives to be sold in Europe.  In practice, even if this were the case, it can be difficult to source the required certification from a Manufacturer, or Dealer network that invariably views imported drives as 'grey imports'.  This is particularly the case with outboards.

All other boats, including higher speed (planing) craft not fitted with drives which have integral exhausts, currently need to be tested by the importer in accordance with one of the methods outlined in the ISO 14509 series. 

  • ISO 14509-1 Pass-by Test - This is a relatively simple pass by test which records the maximum sound produced by the boat as it passes a microphone at a distance of 25m.
  • ISO 14509-2 Reference Craft Test - This allows craft similar to those perviously tested (ie sister ships with similar engine/exhaust configuration) to reuse certification from tested craft.  In practice this is seldom available.
  • ISO 14509-3-2009 Predictive Test - This uses measurments taken within the cockpit, combined with formulae derived from the SoundBoat project to predict the values which would otherwise be derived from a ISO 14509-1 Pass-by test.

Under current legislation, almost all boat and engine variants must be tested.  This means that if the same boat is offered with different engine options, each option will need to be tested.  Some Notified Bodies may allow minor changes without further testing, if the original boat was significantly below the statutory limits.  ISO 14509-2 provides a theoretical approach to using reference craft, subject to minor variation.  In practice however, few if any reference craft have been documented and so this is normally not available to the importer.  We will thus not consider this further here.

ISO 14509-1 Pass by testing

The principles behind pass by testing are straightforward enough.  The test boat has to pass a microphone at a distance of 25m at full speed up to a maximum of 38 knots.  The peak sound (A-weighted, Slow) measured at the microphone, averaged over three consistent runs per side, is the figure used to determine compliance.  This is set at a maximum of 78dBA for a twin engine boat and 75dBA for a single engine boat.

There are 2 practical ways of testing depending on the facilities available at the preferred test site:

1.  Using a microphone mounted on a jetty or other fixed platform

2.  Using a microphone mounted on an anchored/slow moving support boat

Clearly the practical aspects vary by size and this type of testing becomes increasingly difficult (and dangerous) as the size of test craft increases.  This is particularly apparent for craft over 15m in length, whose sheer size and presence can make sitting in a small dinghy 25m off, with you thundering by, quite a daunting prospect.

If testing from a support boat, two boats and crews are needed.  It is often not possible to anchor at the test site (especially if a Norwegian Fjord) so our preferred approach is to stream a marker buoy on a floating line ( e.g. wakeboard rope) from behind a slow moving support craft (ideally driving into any tide), cutting the engine of the support craft as the  test craft approaches its run.  The momentum in the support craft keeps the line tight, to ensure the correct distance is maintained.  The line is typically measured to 23m (ie 2m less than the required 25m) so that so long as the crew ensure the test craft passes within 2m of the marker buoy, the test craft will be within the 25m required by the standard.

Generally speaking the larger the support craft the better, as in addition to maintaining momentum they tend to offer a higher and more stable platform for noise metering.

Typically, setting up for testing takes about an hour and the test itself takes about 2 hours per boat.  With briefing and boat transfers included, a minimum of half a day should be allowed.  Once the equipment is in place, the incremental cost for testing more than one boat is relatively small, so we would recommend that as many boats as possible are tested at the same time to keep the overall cost down.

Test site

The test site itself needs to be very sheltered and to have approximately one nautical mile of unobstructed water for boat manoeuvring.  This is to allow the boat under test to have adequate room to turn, build up to full speed, run out and turn again, all with a margin of safety.  Even if it is not strictly required, we ask you to inform the (US) coastguard and any other statutory authorities that testing is being carried out.

Whether testing from a support boat or a fixed platform, care also needs to be taken to ensure that other boats are not inconvenienced or endangered.  Sheltered sites attract small boats and their safety must be taken into account at all times when testing.

Safety of the support boat, the boats under test and other water users remains the responsibility of the skippers at all times.  Gablemarine staff will advise on positioning and will deploy all equipment but the skipper always remains in charge.


The most significant constraint to testing is the weather.  At the moment, the standard limits wind speed to 7m/s (about 12 knots) and wave height to length/50 (i.e. max 500mm for a 24m craft, 200mm for a 10m craft). No precipitation is allowed so testing in rain or mist is not possible.

ISO 14509-3-2009

Introduced in 2009, but based on data from the European SoundBoat project which ended in 2005, this approach is best suited to larger craft (>11m) with a maximum of two chines and a square transom.  

The two major advantages of this approach are firstly that the measurements can be taken from within the test craft (ie no support boat required) and secondly that the testing is less constrained by weather conditions.

The sound levels are recorded at that same speed as for the Pass-By test.  The meter is positioned on an arm 1.2m above DWL and 1.2m from the hull/transom edge, in a series of seven locations, one on the centreline and three symetrically on each side.

Various allowance apply but the aim of the test is to predict the values which would be measured if a ISO 14509-1 Pass-By test had been performed.

Written By: Rowland Smith

Rowland Smith is a Naval Architect and founder of Gablemarine.  His industry experience includes Lloyds Register, British Shipbuilders Hydrodynamics Ltd, Cammell Lairds, BP Shipping Ltd & Conoco.  He has a degree in Naval Architecture, a Diploma in Marketing (CIM) and an MBA (Cranfield School of Management).  He has also held Director level positions in a number of technology and engineering companies, including CEproof, which provides RCD compliance software to builders. 

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