September 24, 2009

Bright Lights, Big City, Bad Power? More Adventures with Audio Prism Noise Sniffer.

Bright Lights, Big City, Kuala Lumpur, home to 3.5 million Malaysians. That's the official figure, add another million or so if illegals are to be counted, He!He!

Using the very same method I described on my earlier Audio Prism Noise Sniffer post for checking RFI/EMI noise riding along the power lines to my home, I've decided to check out other areas of Kuala Lumpur, where friendly homes are open to my probing. The list is not exhaustive, and does not cover many areas, but I believe it's a fair representation of overall power condition within the Kuala Lumpur and Klang Valley in general. You get the idea.

As usual I begin with checking the room ambient noise before doing any further measurement. Whilst there are rooms quieter than the 50db of the SPL meter limit, it'll not show. But all room's ambient noise taken is somewhere between 50db(quietest and SPL meter limit) and 54db(noisiest). Now 4db may not seem like a lot, but I must stress that our average system playing music at average SPL peak of 90db volume in a 50db ambient room may only require 25Watts of theoretical amplifier power, playing the same music it the same 90db volume with the same system in a 53db ambient room will require the use of a theoretical 50Watts amplifier, for us to hear the same volume and music dynamics. So a quieter room is a better room for hifi enjoyment.

With the room equation out of the way, lets see if your area has noisy power lines.

AREA: LOWEST db - PEAK db

Putra Heights, USJ: 92 - 112

Petaling Jaya, Section 13: 92 - N/A

Petaling Jaya, Bandar Utama: 88 - 102

Puchong, Bandar Putri: N/A - 102

Serdang, Seri Kembangan: N/A - 112

Kuala Lumpur, Jalan Ipoh: N/A - 113

Kuala Lumpur, Seri Hartamas: N/A - 105

Subang Jaya, SS17: N/A - 112

From the chart above, where possible like Odiosleuth's and my own place, I managed to measure the lowest A/C power noise(88db and 92db), which are typically Sunday afternoons, and peaks which are usually week day evenings, at (112db and 113db) when factories are not closed yet, or operating at night shift and at the same time, many people are already back from work, at home turning on their lights, plasma TV and every other home appliance you can think off. If you take the peak levels recorded, deduct with the typical room ambient measurements, that will translate to between 40-60dbs of RFI/EMI noise riding along your power supply lines.

For most of us listening to our hifi system at 90-95db music peaks, which is already very loud(this I've been told off by countless people! He!He!), which I measured in my own room with peak music playing. Having power supply lines noisier than our peak music volume only make things very unpleasant to listen to.

The tools for the job, Audio Prism Noise Sniffer and an analog SPL meter.

Of course, prior to this most of us would never know how bad the situation was, because the noise was inter weaved in to our music, showing it self as grainy high frequencies, irritating sibilants, edginess in the music and may even result in indistinct and unstable imaging. Hence over the last two decades or so, audiophiles begin to find ways to solve this A/C power supply noise issue.

Many have advocated a separate and dedicated power line(from 3 phase supply, if possible), pulled direct from incoming, all the way in to the hifi room where the MCB panel is no more than 6 feet away from the power point you plug the hifi system in to. I did not get a chance to measure a home with this power layout for hifi room, so I cannot confirm nor deny it's effectiveness.

The other more common way for most of us is to power our hifi system via a power line conditioner. In my case as exhibited earlier, some other auxiliary equipment were also used to achieved a minimised, or noise free power line as close as possible result. With that in mind, armed with the Audio Prism Noise Sniffer at hand, I went about checking various PLC systems available in the market and their effectiveness in power line noise reduction. Stay tuned.

Audio Prism is sold by Hi-Way Laser, contact Kenny, tel: 019-2813399

2 comments:

Rabin said...

I am wondering if you going about this the right way. The sniffer does have a volume control and no matter what setting you have it at, its still amplifying the signal so that its loud enough to be heard via the built in speakers. What you are measuring is that amplified noise.
Its unclear how much of that noise actually gets into the audio chain for it to be significant given that every component will still be influenced by its own signal to noise ratio with some doing better than others.

Have you tried measuring the ambient level at listening position or at a fixed position in front of the speakers with and without the IsoPlug (or with/without any other PLC) at normal listening volume?
I would think this would be more representative of the noise present and/or noise reduced.

Big E said...

Rabin,

I agree, my methods are psuedo-scientific at best, however that was the method I had decided to use after consulting an electrical engineer and a pro AV installer.

The Noise Sniffer on the surface has a volume knob, but upon closer inspection, it's actually a sensitivity knob. The instruction on the Noise Sniffer asked to start with volume at 12'o clock, and if no sound is heard from the built in speaker, turn volume further up.

Here's another interesting fact about the measurement method used. Irregardless of volume setting on the "volume knob' of the Noise Sniffer, at 12'o clock or full volume, if there's noise, the reading on the SPL meter would be the same, even if the sound is somewhat louder or diferent tone. Sound pressure level and volume loudness though related are perceived diferently, by us.

Anyway, the whole idea for comparison is that the measurement method is the same thru out the excersice so that the figures obtained are representitive, valid and fair given the bigger picture.

I am just trying to point out the level of RFI/EMI noise riding along our power lines in KL.

How much of those get in to our hifi equipment and manifest it's self as sound gremlins? I would think the answer lies in our equipment's ability to filter the noises out. I know for example, the newer Pass Labs(X series onwards), Ayre and JRDG, all have some form of filter built in to the power supply. Others like the higher end series Krell and Mark Levinson has built in re-generators in their power supplies.

To use your suggested method for the sole purpose of knowing much much RFI/EMI noise there is in KL's TNB power lines would invariably allow each of the equipment's ability in all diferent locations to influence the results either way. Hence, it was best to measure only from the Noise Sniffer, plug direct in to the wall power point, free from the system's influence.

I hope my explanation is valid and fair.