résultat analyse acoustique de mon home studio

The ETC shows reflections from the room boundaries, the desk, or diffraction from the edge of a speaker box. The level and arrival time of reflections show if they are welcome or not. Very broadly speaking it would be nice not to see any above -20dB during the first 20mS. As the reflections are directly visible over time, Decay Rate and ratio of Direct Sound to Reflections and the later room noise are readable.

What we are interested in is observing the early reflections, when they arrive and at what relative level. In a control room, we strive to minimize reflections arriving too soon (approx. 15-20 ms) after the direct signal and after a time period called the ISD-gap, we usually want a diffuse field (lots of dense reflections). Unfortunately, a bit like the opposite of what the above ETC shows. In small rooms it might be problematic to achieve a good termination of the ISD-gap but at least one should try to minimize the level of reflections within approx 15 ms. You should try and figure out what causes the reflections arriving at about 2-3 ms in your room and absorb/redirect them.

The second is the energy time curve (ETC), which is a plot of amplitude in db against time (typically measured in milliseconds). An energy time curve shows how sound energy decays in a room. From an analysis of the energy time curve much can be deduced, including the level of reflections relative to the direct sound and the time it takes for sound to decay within the room. Zero on the time axis, and the highest peak on the magnitude axis, represents the direct sound from the speaker. The plot below shows how level changes over time, with each peak being due to a reflection from a nearby boundary such as the floor, celing or side walls. This clearly shows that there are a large number of reflections in a typical listening room and that sound does not always decay evenly. A very important point to remember is that ETCs are spectrally blind (i.e. they contain no information as to the spectral content of the reflected sound). Analysis of the spectrum of reflected sounds is often critical to determine appropriate acoustic treatment.