Reverberation Time Variation with Frequency - November 30th, 2008

By simply looking at Sabine’s equation, one can clearly see that the reverberation time of home cinema installations depends on the volume, surface area and the average absorption coefficient in the room. However, the absorption coefficients of any acoustic wall panels are not constant with frequency. This means that, assuming that the dedicated home cinema has a constant surface area and volume, which is not an unreasonable assumption, the reverberation time in the room will also vary with frequency.

This will subjectively alter the timbre of the sound in the home cinema due to both the effect on the level of the reverberant field, and the change in timbre as the sound in the room decays away. As an extreme example, if a particular frequency has a much slower rate of decay compared with other frequencies, then as the sound decays away this frequency will ultimately dominate and the room will ‘ring’ at that particular frequency.

The sound power for steady-state sounds will also have a strong peak at that frequency because of the effect on the reverberant field level. Materials used for constructing acoustic wall panels for all custom home cinema installations will always have some absorption coefficients, shown as a function of frequency. These are usually presented over octave bands. One could argue that third octave band measurements would be more appropriate psychoacoustically, as the octave measurement will tend to blur variations within the octave which might be perceptually noticeable.

In many cases, because the absorption coefficient of the acoustic treatment varies smoothly with frequency, octave measurements are sufficient. However, especially when considering resonant structures in dedicated home cinema installations, more resolution would be helpful. Note also that there are often no measurements of the absorption coefficient below 125 Hz, this is due to both the difficulty in making such measurements and the fact that below 125 Hz other factors in the home cinema room become more important.

Filed under: Technical Articles — admin @ 9:27 am

Escient SE-500i Music Server - November 29th, 2008

Today’s multi room audio installations require multiple sources to be distributed throughout the home. The biggest challenge with audio distribution is to be able to digitally store all content, in order to allow easy access from every room. Escient music servers are the pinnacle of digital media management systems. There are two versions available providing 160Gb and 500Gb internal storages, respectively.

You can simply record all CD’s to the Escient’s internal hard drive and let the music server automatically connect to the Internet to identify each CD. The Escient music servers provide the user with the artist and album name, genre, song list and cover art. Multiple touch panels can retrieve all information throughout the home, creating an easy to use multi room audio system. Escient music servers can integrate with various home automation products like AMX and Elan.

The Fireball SE music servers can be of course used as a stand-alone audio source and replace an existing CD player. Philips touch panels now offer great integration with their TSU9600 and TSU9800 control touch panels, allowing for absolute control and ease of use. Multiple Escient music servers can be used together, if extra storage and multiple streams are required. IP based multi room audio systems like Netstreams can distribute up to five simultaneous audio streams from a single music server.

The free Escient Fireball PC software shares all music stored on a PC with an SE music server. Anyway you look at it, the Escient SE music servers are the easiest and most affordable way to enjoy your music now and in the future.

Filed under: Product Articles — admin @ 10:46 pm

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