No. During normal operation of most of our BACtracks, after you turn the unit on, there will be a countdown while the sensor warms up. Once it reaches zero and you start blowing into the unit, it will emit a long beep sound, which indicates that it is receiving a good, strong breath sample.
When the unit has enough sample to analyze (about 5 seconds later), the beep will stop, and you might hear a click sound—this indicates that the unit is analyzing the sample. A few seconds later, the LCD will display your BAC estimate.
The only BACtracks that don't emit a beep while receiving an air sample are the B70 and BACtrack Mobile.