Yes, the audio signal is still in the HDMI Out. In my case, the audio signal (RCA Out) goes to the music system. To mute the projector (HDMI audio), I simply plugged a cable without a signal into the Audio In.
This is actually already stated in the product description. See also the product image. 3 options - SPDIF via Optical Out - SPDIF via RCA Out - Analogue via stereo mini-jack out