The D90 is a 12.3 megapixel single-lens reflex digital camera made by Nikon, which makes beeping sounds when you use it to do certain tasks. For example, the camera beeps when you use the self-timer to take a group picture, or when you use the auto-focus feature while composing a picture. If you find the beeps distracting or otherwise need to take your pictures in silence, you can easily disable the beep sound on your Nikon D90 camera.
Press the "Menu" button on the left side of the back of the Nikon D90. The camera's menu appears in the LCD display.
Press the multi-selector button down to highlight the "Custom Settings" tab, and then press the "OK" button to select it.
Press the multi-selector's "Up/Down" button down to highlight the "Timer/AE Lock" tab, then press the "OK" button. Press the multi-selector button down to highlight the "Beep" option. Press the "Right/Left" button right to change the "Beep" option to "Off," and then press the "OK" button.
Press the "Shutter Release" button halfway down to exit the menu and return to shooting mode. The "Shutter Release" button is located at the top of the camera on the right.