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.

S-330 marine air horn

Kahlenberg S-330 marine air horn

The Kahlenberg S-330 marine air horn provides a fully IMO compliant and ABS certified sound signal for leisure boats and commercial vessels up to 75m (246ft) but in a very compact and efficient package.

The size and efficiency of the S-330 is a result of detailed design effort on its special alloy diaphragm that produces the requisite levels of sound for very modest air consumption. The horn has been extensively tested and refined in Kahlenberg’s own anechoic test chamber.

The performance of the horn has subsequently been certified by ABS and you can view the model’s ABS certificate below.

As a result of this design effort the S-330 outperforms competitors in terms of its air consumption and form factor. This also leads to corresponding benefits below decks as extremely small DC or AC compressor systems and tanks can be utilised while providing ample capacity to IMO requirements for all required signals.


This makes the S-330 an extremely attractive proposition for vessels where weight and space saving is a consideration or where a compact IMO compliant back-up whistle to the vessel’s main sound signal is required.


As with all Kahlenberg sound signals the S-330 is built in quality materials - spun brass and cast bronze, with a special alloy diaphragm. It can be supplied in sky white powdercoat or chrome. It is constructed with aesthetics in mind to match the best superyacht finishes, with no ugly seams in the bell.

Because of the choice of design and materials you can expect extremely long and reliable service.


The fundamental frequency of the Kahlenberg S-330 marine air horn is 330Hz and its SPL dB(A) is 136dB. Air consumption is 9CFM (4.2 l/s) @ 100psi (7 bar). It works on a wide range of pressures from 50-200psi (3.5-14 bar). It measures 18.7in (475mm) long with a 6.5in (164mm) bell.


Kahlenberg S-330 marine air horn technical information (PDF 476Kb)

Kahlenberg S-330 ABS type approval certificate (PDF 25Kb)


Further information

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