Description of SMARD

SMARD is a database containing approximately 18 GB of 24 bit audio recordings at a sampling frequency of 48 kHz. Below, a description of the database is given.

The Room

The recordings have all been made in a 60 m² multichannel listening room at Aalborg University, and a sketch of this room is given in Fig. 1. We removed the carpet on the floor during the measurement campaign. The room is box-shaped, symmetrical, and has been measured using the Brüel & Kjær Type 2270 to have a reverberation time of approximately 0.15 seconds.

Equipment

Recordings were made for various combinations of different loudspeakers and microphone arrays. As detailed in the equipment section, three loudspeakers were used. The Brüel & Kjær OmniPower 4296 and the Brüel & Kjær OmniSource 4295 are both approximately omnidirectional loudspeakers within a limited frequency range. The OmniPower 4296 loudspeaker can emit more sound power than the OmniSource 4295, but can only be considered omnidirectional over a narrower frequency range. The directional loudspeaker is a conventional 3'' speaker in a wooden cabinet.

Up to 22 G.R.A.S. microphones were used in various array configurations. The simplest array was just a single microphone. The other array types were uniform linear arrays (ULAs), uniform circular arrays (UCAs), and an orthogonal array. Finally, a dummy microphone, which is simply a capacitor mounted on the microphone pre-amplifier, was also present in all recordings. The recordings from the dummy microphone can be used to inspect electrical noise, cross-talk, etc. Except for the loudspeakers, the microphones, and the arrays, all measurement equipment was situated in a control room adjacent to the multichannel listening room. A list and pictures of this equipment can be found in the equipment section.

Measurements Configurations

Measurements were made for a total of 48 different configurations. Each configuration is enumerated by a four digit number of the form ABCD where the first and most significant digit A denotes the type of loudspeaker; the second digit B denotes the position and orientation of the loudspeaker; the third digit C denotes the type(s) of microphone arrays; and the least significant digit D denotes the position and orientations of these arrays. Table 1 summarises these configurations and depictions of all the configurations can be found in the download section. 

Audio Segments

For each of the 48 configurations, a total of 20 audio segments were played and recorded. As listed in Table 2, seven artificial signals, six speech/vocal signals, and seven musical signals were used. The artificial signals were all created in MATLAB and a description of them can be downloaded here. The speech and musical signals consist of both reverberant and anechoic signals. The signals from the EBU SQAM CD are reverberant signals whereas the signals from the TSP speech database and the musical instrument samples (MIS) database are anechoic signals. As it can be seen by following the above links, all of these databases are freely available online for research usage.

For every configuration, the temperature inside the multichannel listening room was measured and stored before these 20 audio segments were played. For each of the audio segments, all of the microphone recordings and a loopback of the loudspeaker signal were stored in the database. A pause of two seconds was added between the segments to ensure that the sound field within the room was approximately stationary before the next segment was played. The first audio segment was just five seconds of silence. The recordings made with this input signal can be used to inspect the stationary acoustical background noise.