After many months of experimentation, the first of the PC component sound recordings have been released in the 2nd page of the Nexus PHT-3600 review. There is a small number of recordings of two fans.

I would like to get feedback from people on the sound level calibration / comparison described. How well does it work for you & what do you think the limitation are for you?

Like anything else new, it will take time to train ourselves to distinguish the real differences revealed in these additions to SPCR's testing repertoire. The human auditory filtering process is highly adaptable. The sophistication of the brain's innate processing capability allows people to accept considerable variations in sound quality whereas there is little room for error with regards to vision. This is easily proven. Since the days of the most primitive sound recordings, people have happily gone to the movies and endured sub-par audio quality but objected vociferously when the projectionist misfocused on the screen. Learning to appreciate sound quality is an acquired ability but, once acquired, is recognized as being highly desirable. As we who have obsessed over each little reduction in overall noise level in our systems have learnt, there is no going back. Now I practically run from the room when I'm subjected to the noisy computers of friends and family. How can they stand the noise, I wonder?

An absolute audio reference is probably impossible but might each sound recording report include a benchmark against which to make a comparison? For example, if it's 120 mm fans that are being compared, SPCR could indicate that fan XYZ is the quietest fan in the test and possibly cut back and forth between the reference and the comparison fan in each recording sample? Audio memory is notoriously poor, an aspect of the aforementioned capacity to "listen through" bad sound.

Despite the learning curve involved in making meaningful comparisons, this new addition to the test reports is a great step forward. Congratulations and well done!

Mike, by writing the above, I did not mean to discount the calibration technique with the Panaflo fan you described in the Nexus PFT-3600 review, but instead was thinking of how best to deal with the fact that most people will probably not be willing or able to create an audio facsimile of the SPCR Lab environment. I expect that taking the time and effort to do so will be reserved for the hard core SPCR enthusiast. But whatever people chose to do, the mere fact that you have provided that calibration technique, proves to me, once again, that there is a world of difference between SPCR's professionalism and the amateur methods of most of the other review sites!

Well, I am not sure about professionalism... but I am sure that if you play back the sounds too loudly or too softly, your impressions will be misleading. (Get close enough to someone's belly and the human body can sound like house plumbing!)

As I wrote, audio fidelity most certainly includes correct playback level. The bandwidth of fan sounds is fairly narrow, so the freq range of the playback system is not critical -- though flat freq response and linear dynamic range are important. (Despite subjective impressions of high pitched whining and so on, the bulk of it is in the 30~400Hz range, and "high pitched" overtones are still well under 10kHZ.)

I am working on several other reference sounds -- certainly more reference fans, including at least one noisy one. The thing I am looking for is a truly universal reference that is accessible almost everywhere, a sound that everyone is familar with and has in their house or office, but it's hard to think of something appropriate. I considered such things as a toilet flush, a running shower, a blender at low, kettle on boil.... but rejected them all because ther's too much variance between mine and others'. Any ideas? (Now please don't get too silly OK?)

Mike, one of the hallmarks of taking a professional approach is not being afraid to admit that there is still much to learn and improve. Your modesty is both commendable and reassuring!

To help with establishing a universal reference, how about providing a noise comparison chart in each report of a range of "typical" sounds? We're all familiar with charts that illustate relative noise levels from, for example, a turbojet engine down to a quiet room at 3:00 AM. A more narrowly focused chart just for SPCR could be at least a general guide?

Racking my brain for a universal reference familiar to all of us from our offices and homes just underscores the wide variability between noise emitters. I remember wondering why certain carpet cleaners were so noisy and reading a Hoover spokesperson's claim that "housewives need to feel that their machine is powerful enough to get the job done." Perhaps that has been one of the underlying attractions of certain noisy multi fanned gamer computers?

No question about it. PSU and HSF had this approach for a long time, and gamers bought right into it. I've heard this directly from the manufacturers and sellers.

how about a ringtone?

The default ringtone of Nokia (Siemens, and some other popular cellphones) at the default volume.

i have a small electric space heater that sounds *exactly* like a 120mm Evercool... kind of creepy since the heater doesn't sound much like a typical fan.

hard to think of "standard" sounds. standard pen click? vacuum sealed pop top? fly buzzing?

How about an A-Bomb going off? Or a car alarm?

Honestly, I dont think there is a way to have a standard reference noise, as each person has been exposed to certain experiences and such.

The only thing I can think of is turning your speakers to max volume, and setting the system volume to the minimum and then playing it. No, it won't blow out your speakers.

Interesting problem.....probably without a 100% exact solution. How about something of a universal size/weight/material such as a standard marble, dropped from a specific height, onto/into a universally available object, such as a shot glass or something similar.

The idea being a sound that can be duplicated more or less exactly using easily available materials.....

My reference sound suggestion is one hand clapping.

But seriously, what about the POST beep?

I also think it would be advantageous to record several seconds of the reference Panaflo and then cut to the sample fan. Then we can clearly hear the difference and it doesn't matter what our volumes are at.

Ok, let me get this straight. The idea for a reference sound is to enable you to adjust your speaker volume to the point where when you hear a sound file say from MikeC.....you are hearing that file at the exact volume he is hearing it.

MikeC would post a sound file say of the dropping marble, for instance.....then you would adjust your speaker volume so his dropping marble sound file, and your dropping marble experiment sounded exactly the same.

Then when you heard other sound files from MikeC, you would hear them exactly like he is. I don't think a reference sound should be of an object (a specific fan for instance) that is not available to everyone.

The dropped marble is not a good reference sound, because it misses an important property. A reference sound should have a stable sound level over a longer period. You should have time to turn some dials of move some sliders while listening to the sound.

Also it is not necessary to limit it to one reference sound. Mike and his lab assistants could make a 12V in free air sound file of all fans that get tested over time. Even include some for fans like a high speed Delta and a Vantec Stealth. Then it is likely that you have at least one of those to "calibrate" your speakers.

You've got it exactly.

However, there's no avoiding the use of fans for reference files. It's the most common noise source in a PC and most of us end up with Panaflo 80Ls(and some others) sooner or later. Those who want the maximum usefulness from these sound files will get a reference fan sooner than later.

I've come to the conclusion that there is no such thing as a ubiquitous and perfectly consistent noise source in the home or office. Everything makes a different sound at a different level. Your marble idea is on the right path but a huge problem with it is that it is essentially percussive in nature while all the sounds I am recording are pretty much steady state. Very difficult even for highly trained listeners to compare loudness levels between such different types of sounds.

So here are some reference files that I will be making available:

Panaflo 80L in free air at 12V and on the Alpha 8045 HS -- at 12V (25cfm), 10V (20cfm), 8V (15cfm) and 6V (10cfm).
Nexus 92mm fan in free air at 12V and on Thermalright XP-90 HS -- at 12V (25cfm), 10.7V (20cfm), 9V (15cfm) and 7V (10cfm)
Nexus 120mm fan in free air at 12V and on Thermalright XP-120 HS -- at 12V (42cfm), 8.6V (30cfm), 6.1V (20cfm) and 5V (15cfm)
Samsung SP-80 -- bare on kitchen counter, 3" distance, idle / seek; completely decoupled on foam on same kitchen counter, 3" distance, idle / seek.

SPL at 1m will be included with each file.

Yes, the Nexus fans will all be adopted as reference fans for SPCR reviews, along with the Panaflo 80L. All the Nexus fans are truly quiet & smooth, and show very good sample-to-sample consistency. They are basically very low-speed fans that don't push much air, which is generally true of quiet fans, but also have very low bearing noise and appear to have been carefully cherry-picked. As most extreme silencers can vouch, consistency is uncommon among fans. In my worst purchase of Panaflo 80Ls, I cherry-picked 5-6 units I felt good about using from a box of 20.

The Nexus 80 would be in the list above, but I managed to break a couple in a nasty lab accident that took out several fans before I had a chance to measure them completely. There should be a couple more in the lab but I seem to have hid them from myself for safekeeping. (It is quieter than the Panaflo 80L but its airflow is lower than the Panaflo 80L.)

I still need at least one noisy reference. Any suggestion for a noisy fan that's cheap & ubiquitous?

Tibors....that marble thing was only an example of one sound/volume that everyone could duplicate. I suppose if there were a sufficient number of different fan models as a reference sound(s), most SPCR readers would be covered. But what about non-computer geeks visiting SPCR who might want to casually do this sound comparison?

If there were an easy-to-duplicate reference sound, this whole sound comparison thing could be a big hit.

"How quiet is your computer? Visit SPCR to find out."

I did have one idea that I canned:

Take a 2 liter plastic pop bottle, fill it with water, then flip it upside down into a plastic jug that has a top opening slightly smaller than the diameter of the bottle and let the water drain into the jug. The resulting noise is pretty consistent. Two big problems with this:

1) Water near your PC/monitor/speaker is not a good idea. I spilled some water on the kitchen counter every time I tried it.
2) Different plastic jugs will have a big impact on the noise.

Like Mike, I don't know any "household" sounds that meet the needed criteria.

• Easy reproducable
• Availlable reasonably world wide (at least in the western world, where most SPCR readers originate)
• constant over at least 15 seconds

I looked around in my two room appartment and I couldn't think of any. If someone can think of one, I see no objection to add it.

They won't get into it this deep unless they're audio/sound nuts, and if they are. they'll go ahead and get a reference fan. The rest will probably be happy to have the sound files to compare anyway.

Let's not lose sight of the fact that even if the absolute loudness level is not matched, you will still get very useful comparisons as long as you leave the playback volume controls untouched for all the sound files.

My advise to those who don't have one of the reference fans: Set the volume so that you can just barely hear the quietest (10cfm) files from a meter away. That should be pretty good.

BTW, I guess nobody noticed yet that the reference fans listed above show the Voltage required to reach specific CFM? Yup, part of the fan research I've been doing over the summer. Note particularly how the Panaflo 80L actually needs slightly less voltage to reach the same CFM compared to the Nexus 92.

Here are some ideas:

Drop a CD (something else) from a given height to a wooden floor.
Stapler
Write on a chalk board.

I think the reference fans and hard drive should be sufficient though.

How about the gamer's delight, one of the Deltas, perhaps the highest speed 80mm? Just listening to one of those would be an education in itself regarding the desirability of quiet computing!

Mike,

How about a Vantec 80mm? I mean EVERYBODY makes the mistake of buying one before coming over here, right?

I've got a question/suggestion. Why not assume that people can get access to a cheap Radio Shack SLM and provide pink noise that is recorded by you to be 60dB (or whatever is an appropriately loud noise that can be measured by relatively cheap instruments). This method would be far more accurate than anything dependent on two exact samples.

Oh, and using Ogg Vorbis could save you bandwidth.

Ha....that's a good idea. I've got one of those meters, and it seems to be relatively accurate, but only goes down to 50db. A 60db sound file would make for easy calibration.

60 dBA pink noise & cheap SLM -- maybe. I suspect Panaflo fans are MUCH more widely available than SLMs, regardless of their expense/sophistication.

There might also be a technical problem on my side with this: The mic preamp & all the input sensitivity on every hardware & software control through the system is at absolute max gain to ensure that very quiet (<15 dBA/1m) sounds can be recorded and played back without the noise floor of the system (shhhhhhhhh) swamping out the quiet sound. A 60 dBA/1m input would probably translate to >80 dBA at 3". This may exceed the dynamic range of the system -- ie, it might overload the front end. Not sure, will have to try it. (You have to measure it at least 1/2 meter away, otherwise, the reading is inaccurate -- usually boosted in the lower mid/bass.)

I obtained an inexpensive SLM with high hopes but found, unfortunately, that its lowest measurement threshold was far too high to gauge the noise levels in my system. I'd planned to do "before" and "after" modification measurements.

Perhaps, an enterprising manufacturer will awaken to the idea that an inexpensive SLM with high sensitivity for low sound levels has a market niche now that people are increasingly aware of the detrimental effects of noise pollution. Admittedly, there are many technical and marketing challenges in making such a device both inexpensive and ubiquitous enough for more people to want and use one.

I'd like to know why my idea of the cellphone ring is not considered by anyone. Is it soooo bad that does not even need an explanation?

Perhaps it's because we all set our cellphones to the vibrate mode?

All joking aside, my experience of hearing cellphones is that the intensity of the noise varies according to the volume level set by the user and, naturally, the ambient noise conditions in which they ring. I'm no auditory expert but I'd also guess that a steady state rather than intermittent sound would be more suitable?

Ain't no doubt about it, MikeC, this is an interesting audio puzzle that you've set before us.

Cellphones would work.....

...if we all had the same brand, with the same ringtone, set to the same volume.


Here's an idea... Kazoo's!

Here's my wacky concept: When you donate for Patron status, you can opt to receive an "Official SPCR calibration tool" (aka: a kazoo), for a small additional fee to cover shipping and handling. Perhaps the "Calibration tool" could also be emblazoned with the SPCR logo.

A puzzle it may be, but there is a pretty simple if rough fix, which I posted to the article in an edit yesterday:

If you don't have a Panaflo 80L fan, listen to the quietest of the above sound files (the Panaflo 80L at 7V), set the playback volume to the point where it is just barely audible a meter away, and don't touch the volume setting when you listen to any of the other files. That will be reasonably close to the actual recorded sound levels.

It's based on the fact that a Panaflo 80L at 7V is just barely audible a meter away in open air in my office -- at least during the day when the ambient noise leve is somewhere around 22-26 dBA. If your hearing sensitivity a much better or worse than mine, then this won't be quite right, but it will be close enough that you'll certainly get the gist of each noise maker's real noise relative to the others that have been recorded -- as well as to the noise sources you have.