Disclaimer: I'm not an acoustics expert by any account; this is just to share some accurate sources of information I have found helpful, and revise the information for myself.

As the home studio has become increasingly central in carrying out professional work, calibrated monitors are necessary to ensure that work will translate accurately on different, larger systems. A mix that sounded nice and balanced on the home set up, is suddenly boomy and muddy on a larger system.

It all comes back to the Fletcher-Munson curve. At lower listening levels, we can't perceive bass and high frequencies very well. At around 80dB SPL, the curve flattens out and our perception of the frequency spectrum becomes more balanced. Meaning you won't be trying to compensate using EQ boosts, and unintentionally muddying your mix.

Sound on Sound have a great, free article on steps for calibrating. Note the table at the end that advises SPL calibration levels depending on room size. The 83dB SPL figure is often bandied around forums, even though it only applies to larger rooms with mid to far field monitors; it originates from Dolby calibration of dubbing stages. In a small room with near fields, 83dB SPL is deafening.

The SPLnFFT app came in handy as an iPhone SPL meter, and has according to research papers, come out as one of the more accurate SPL meter apps.

I recently re-calibrated my speakers in a new room to the 74dB SPL level which is appropriate to the cubic volume of the room. I also hung acoustic foam on the walls to help dampen the flutter echoes in the room, and have some bass traps in the the corners. It's still far from a perfect room, but treatment works exponentially - a little will go a long way. Acoustic treatment is vital if you're to benefit from monitor calibration, otherwise you'll still end up EQing incorrectly as you eliminate frequencies that are interacting with the room.

The MP3 codec is often regarded as the spawn of Satan by audiophiles. For me it was always something that was a product of logic. It began out of necessity, to transfer audio over the web at a time when broadband was not yet prevalent. Then, it allowed music collections to fit on to the less than spacious drives of portable media players.

There is now a generation who have consumed music almost entirely in MP3 format

After viewing a talk by Bob Katz on modern mastering in which he played the detritus left over by the MP3 codec, I was curious enough to have a listen for myself on a number of sources. Using four examples, from Classical to Modern Pop, it becomes obvious how modern mastering process affects digital compression.

'Blue Danube' suffers little from the process, due to the gentle mastering that it would have received. It is preferred with Classical pieces such as this to leave the dynamics generally unaltered.

'Never Going Back Again' and 'Sunday Morning', both tracks from the pre-loudness war era, don't suffer too badly; but there is definite distortion and aliasing in the top end.

Finally, you can hear for yourself the trainwreck that is 'Telephone', crushed and brickwall limited to compete with the loudness levels of the charts.

**Audio has been deleted since**