User manual SONY MDR-NC300D

[. . . ] You can attach the headphones to the supplied holder to keep them together. the power switch is located on the battery box. When power is turned on, ambient noise is reduced, and you can listen to music more clearly at a lower volume. While using the headphones, you can attach the holder to the headphone cord. [. . . ] Clean the headphones with a soft dry cloth. Do not leave the jackplug dirty otherwise the sound may be distorted. Be sure to bring the headphones to the Sony dealer when requiring a change of earbuds or repair work. The CE mark on the unit is valid only for products marketed in the European Union. Do not leave the headphones in a location subject to direct sunlight, heat or moisture. To clean the earbuds, first remove them from the headphones, and then clean them with water and mild detergent. After cleaning, dry each earbud carefully before use. The earbuds will need to be replaced from time to time. If they are worn out by daily use or longtime storage, replace them with new ones. If you fell drowsy or sick while using these headphones, stop use immediately. As headphones reduce outside sounds, they may cause a traffic accident. Also, avoid listening with your headphones in situations where hearing must not be impaired, for example, a railroad crossing, a construction site, etc. The model number is located at the front side of the battery box. Refer to them whenever you call upon your Sony dealer regarding this product. The noise canceling function may not work properly unless the headphones are put on firmly. You can use the headphones even without turning on the power. In this case, the noise canceling function is not active, and the headphones operate as passive headphones. After you turn on the power of the headphones, you may hear a slight hiss. This is the operating sound of the noise canceling function, not a malfunction. In a quiet place, or depending on certain noises, you may feel that the noise canceling function is not effective, or that noise is accentuated. [. . . ] In this case, turn off the power of the headphone. Interference noise can occur from nearby cellular phones. Should this occur, locate the headphones further away from the cellular phone(s). Noise canceling headphones reduce ambient noise, and provide a quieter environment to enhance audio entertainment. [. . . ]