Air Leak Detection (ALD) & Stethoscope (ALS)

The picture shows a typical end-of-line test setup for active speaker systems such as a multimedia, Hi-Fi or portable speakers using KLIPPEL Analyzer 3 equipped with Laser Card and XLR Card. The main test microphone is located in the front for testing typical parameters such as frequency response, THD, Rub&Buzz distortion etc. using the SPL – Sound Pressure Task.

In order to detect loose joints, enclosure defects or irregular port noise, leakage testing can be simply integrated directly into the sweep test by activating the ALD option in the SPL Task without adding any extra test time. To make sure that rear defects and leakage problems are detected reliably too, another test microphone may be placed at the back of the speaker for an additional ALD test step. Up to four microphones can be used for a single shot test. During the complete test sequence, the ambient microphone outside the test chamber detects ambient noise disturbance reliably and triggers the auto-repeat mechanism for single test steps, if necessary.

Detecting air leaks in large speaker systems with only one microphone suffers from acoustical shadowing of the high frequency leak noise. Locating multiple microphones around the device under test overcomes this problem and the complete surface can be covered for optimum sensitivity.

Sequential Test (Mic Multiplexer)
Using microphone arrays, the number of simultaneous input channels is usually limited by the analyzer such as the KLIPPEL Production Analyzer. In this example, four test microphones are switched by a multiplexer for sequential testing. An additional microphone outside of the test chamber monitors ambient noise in parallel. The test chamber ensures a low acoustical noise floor for maximal measurement sensitivity while the microphone detects impulsive disturbance reliably.

Simultaneous Test (KA3)
Using the KA3 hardware, a high number of input channels can be measured simultaneously using the signal data sharing feature. The QC software currently supports measuring with four microphones at the same time. In case ambient noise is measured (recommended), three other microphone channels are available that may be connected to the Laser Card (IEPE microphones) or the XLR Card (48 V microphones or IEPE using XLR-BNC adaptor). The stimulus signal is played back only once by the source ALD task, which is recording all input signals. The receiver tasks only processes the microphone signals recorded by the source tasks in order to generate the test results and verdicts for all microphones.