In the last meeting of October, the German GS Mark authority ZLS (EK1-AG1) confirmed its decision to enforce sound pressure measurements for all products to which headsets are attached or can be attached. The original measurement standard, EN 50332, is limited to portable audio equipment. However, EK1-AG1 requisites are as said to be the standard for all products to which headphones are connected.

In other words, if an appliance is able to reproduce sound over headphones, EN 50332 compliance has to be proven for successful GS Mark application. Besides MP3 players with fixed headphones, this requirement also applies to, among other items, notebooks, desktop computers, monitors, DVD-players, servers, stereo equipment, and television sets, for which sound output is possible and thus must be evaluated.

EK1-AG1 relies on EN 50332 not only in regards to testing methods, but also in regards to limits. The EN 50332 standard itself consists of two parts: Part 1 is applicable for all equipment to which the headphones or earphones are associated. In such cases a standard noise is played back and the sound pressure is measured with a so-called Head And Torso Simulator (HATS). A judgment of compliance with the standard is given if the maximum measured sound-pressure level is below 100dB.

Part 2, on the other hand, is applicable for headphone outputs. It sets out specifications for the test circuit, with simulation of a standard headset and a load measurement for the respective equipment being tested given (e.g., a monitor). The resulting measured voltage is then compared to the set limit (max. 150mV). Beyond this, Part 2 also describes the setup for cases where a separate headphone is to be tested.

On 1 Jan. 2007 testing principles in accordance with EK1 ITB2000:2007 come into force. An integral component of these testing principles is the testing of electrically operated equipment with headphones and headphone outputs. Besides the testing, a warning statement is required in the user manual along with other safety instructions. This statement must emphasize that the use of headphones other than those recommended / supplied can cause hearing impairment due to excessive sound pressure.

Germany is not alone in implementing sound-pressure measurements within national safety regulations. The French government has also seen the need for protecting its citizens from excessive sound-pressure levels. In this area France is stricter than Germany, laying stringent requirements down in a law for mobile appliances: Article L. 5232-1 of the Public Heath Code. This law has already been in place several years and has been systematically enforced by French authorities, as recent cases of product rejection in France have shown.

It is now accepted industry knowledge that sound pressure generated by headphones is endangering hearing. Besides GS Mark requirements, for liability reasons we therefore recommend staying below established limits, and confirming this via testing at an independent testing house.

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