About Kahlenberg UK

Kahlenberg UK Ltd is the European distributor for Kahlenberg Industries, Inc. providing full European support and local stock for Kahlenberg marine and industrial air horns, sound signals, controllers, air compressors and the company's other products.

Please contact us for further assistance at or on +44 (0)1635 35353

Sound signal legal requirements

IMO COLREGs bookWhile countries across Europe will have local laws that apply to ship and boat navigation, there is a common requirement worldwide for all leisure, commercial and military vessels to conform to the IMO International Regulations for Preventing Collisions at Sea. As Steve Austin, Senior Policy Lead at the UK Maritime & Coastguard Agency (MCA) explains: "The COLREGs apply to all vessels, there is no differentiation between coded and non-coded vessels. Should the whistles prove not to conform then they will need to be modified or changed."

"Whistles should conform to the performance in COLREGs, Appendix III and the appropriate parts of IEC 60945 to EN60945 which deal with the marine operating environment."

All Kahlenberg products meet or exceed these requirements. Many other new and currently installed sound signals are non-compliant and might be breaching maritime law and invalidating insurance cover.

Kahlenberg sound signal FAQs

How do I use this FAQ?

Just hover over the question and the answer will be revealed.

What is a ship's whistle?

A whistle is defined by the IMO as "…any sound signalling appliance capable of producing the prescribed blasts and which complies with the specifications in…these Regulations."

What determines which horn should be fitted?

Your boat's LOA, the sound you want, its compliance, and finally your pocket!

First, take the boat's Length Overall (see another FAQ below) and refer to the IMO requirements for sound signals to determine which Class your boat is.

Second, choose how many trumpets you would like. One, two, or three - the more, the better the sound. For top end super-yachts, Kahlenberg go up to eight trumpets.

Third, verify a Certificate of Compliance will accompany the horns when you buy them.

It's as simple at that.

Should I fit an approved horn just because it's approved?

Certainly not! An approved horn is required on any vessel over 12m, but not at the expense of reliability, functionality or design.

Kahlenberg horns offer a great balance of all of these priorities - and the icing on the cake is that they sound magnificent!

I've just coded my boat for commercial purposes. Do I now need an IMO approved horn?

Whether the boat is coded or not, and provided she is 12m (39ft) or more in length, she must be fitted with an IMO approved horn, irrespective of local regulations and charter or commercial codes.

Does a leisure boat have to have an IMO approved horn?

A common question asked by so many boaters. Yes, vessels of 12m (39ft) or more must be fitted with an IMO approved horn.

What determines the "length overall" (LOA) of a vessel?

So many people have different ideas of exactly what this is.

Officially, the length overall (loa) of the vessel is measured from "the foremost part of the stem to the aftermost part of the stern, including any fixed projections extending beyond the stem and stern."

Our oil tanker has two whistles. One is fitted as a back-up. Are there any regulations for a twin whistle installation?

Yes. If the two whistles are fitted more than 100m apart they must not be able to be sounded simultaneously. If they are fitted within 100m of each other, and if they are designed to be sounded simultaneously, each must differ in frequency by more than 10Hz.

There's been a lot of talk about bells. Is a bell needed?

If you boat or vessel is 20m (66ft) or more, an IMO approved bell must be fitted. This applies whether the vessel is for leisure or commercial purposes.

What is a 'gong' and when is it needed?

A gong is needed if your vessel is 100m or more in length and is fitted in addition to the whistle and the bell. The gong must make a sound which cannot be misinterpreted as that from the bell.

How do I know if my boat's horn meets IMO approvals?

The manufacturer must be able to provide a Certificate of Conformance from an independent Class Society or Flag State Authority such as ABS or Lloyds. This is an important difference from a manufacturer supplying their own certificate stating the horn complies with the IMO specifications.

Bottom line? Without a Certficate of Compliance, the horn in not approved.

My boat was built to the Recreational Craft Directive and is CE marked. Do I still need an IMO compliant horn?

As bizarre as it might seem the RCD does not cover the horn, and hence there is a chance, quite high in our experience, that your horn is not IMO compliant. For further information see the sound signal policy statement from the RCD department of the EC Commission can be seen and downloaded in our Resources pages.

I have a 15m yacht which I use for leisure, only. So what if my horn is not approved?

Now that's a good question. Would the authorities take you to task? Probably not. Are there inspectors roaming marinas seeking offenders? Not to our knowledge.

However one major boat builder in the UK now only fits approved horns since they were advised that if a customer of theirs had an accident, the boat builder may well be found to have been complicit if the horns were not IMO approved.

There is also a question about whether your boat's insurance would be valid in the event of an accident.

When I am in restricted visibility, sounding the horns in the correct manner interrupts my concentration. What can I do?

You can install an inexpensive automatic sound signal controller to make the correct sound signals for you.

My boat is CE marked. Surely this covers the horns?

No it doesn't. Neither the manufacturer nor the owner can hide behind the CE mark.

The horns must be approved which means you must have a Certificate of Compliance.

I keep my 12.5m boat mainly on the canals (inland waterways). Do I still need an approved horn?

Inland Waterways often have their own bye laws which must be met. These may or may not define whether a horn must be approved. So the answer is for you to check your local bye laws.

However, note that if you move from an inland waterway to the sea, you will need an approved horn since your boat is over 12m.

How should I fit my new horn on my boat?

The horn should be mounted pointing straight ahead - not angled down. It must also be mounted as high as possible so there are no obstructions in front of it.

Note that approved horns are LOUD. So don't mount them behind a crew member's head - take care you don't damage the crew's hearing!

Have a read of our Safety advice for Kahlenberg horns.

Why Kahlenberg?

Firstly, Kahlenberg horns are very distinctive in their sound. Secondly, their yacht, motor yacht and super yacht horns look impressive and are the horn of choice of their Captains.

As far as reliability is concerned, Kahlenberg's documented warranty claim is less than a quarter of one percent.

end faq

Further information

Call Kahlenberg UK now on +44 (0)1635 35353 or email