I think it will also help to understand what you wish to achieve. Do you just want to be able to test/review continental equipment without having to replace the plug in which case a Schuko socket strip with a 13A plug fitted would be sufficient? If you are trying to compare the effects of UK and continental mains supplies there are a lot of differences to consider including the use of lower rated three phase supplies to the continental buildings.

One has to be careful - it has been shown that (some) humans are responsive to effects that are quite a long way outside the traditional audio range ( perhaps 10Hz to 20KHz and more like 300 -3000Hz for mobile phone "dalek quality" speech - think mobile 'phone..) 

Correctly instrumented measurements on audio kit need to include looking for effects up to perhaps 50KHz plus that might be attended by apparently imperceptible  roll-off and small phase errors in band that would generally not be noticed.

Also some people 'feel' ultrasound effects, even when they do not report hearing them.

a reference

I'm firmly in the 'if it can be heard it can be measured' camp by the way, but I would say that for a satisfactory measurement one needs a degree of rigour and precision often lacking,

Mike.

OK, so if your ears cannot perceive very high frequencies, how can you perceive them at all?

OK, so if your ears cannot perceive very high frequencies, how can you perceive them at all?

I guess you can perceive the effect of something even if you can't directly perceive the thing itself. If there were two or more high but different frequencies, I might be able to hear the lower frequency interactions (beat?) as peaks and troughs interfere sometimes constructively sometimes destructively. Sort of Fourier analysis in reverse.

   - Andy.

OK, so if your ears cannot perceive very high frequencies, how can you perceive them at all?

The non-linear mixing of modulated ultrasound is a fairly standard way of casting sound directionally - the 'sound' is only re-created at the point of detection.

This chap has done it at the party trick level to 'throw' music with 40KHz transducers.

https://www.youtube.com/watch?v=TQOabMOMGoE

the ultrasound  power levels are higher than I would want to be bathed in but hey-ho.

(google the 'voice of god' weapon for a possible use in warfare, to either instruct some poeple but not others, or to make folk think they are hearing instructions when there is no obvious source,  but there is no public domain evidence to suggest that the idea has left the lab, but in principle it should work.)

Then there is also quite a bit of evidence for sensing ultrasound without inter-modulation though bone vibrations stimulating other nerves not normally associated with hearing.

https://www.sciencedirect.com/science/article/abs/pii/S0378595505000481

This leads to sensations, rather than actually 'hearing' but may be part of the 'feel' of music.

Mike.

Fujimoto may be doing clever things electronically, but the fact is that the tones which were presented to the ear(s) were from 125 Hz to 8 kHz - see fig. 2.

The bone vibrators stimulate the cochlear nerve in the usual way. Ever tried listening to a tuning fork by biting the foot?

Paul Soor said:

… who generally believe, if it can’t be measured, it’s not real. I find their forum interesting but I don’t subscribe to “measurement or nothing”.

Interesting. I used to design rather high end sound equipment (we're talking hundreds of thousands of pound rather than thousands of pounds), and the principle held by the founder of the company was rather the other way around "if it can be heard, it can be measured". We found that a very important principle in equipment design - if somebody could reliably hear a difference (and we got really good at blind testing) we'd go to huge efforts to find what that difference actually meant in signal terms (and we're talking months or years of research here). So that we could then consider that in all future designs. Now we were lucky that we had the funds to do that, most audio companies are run on a shoestring and can't, but also that culture was vital to ensure that conclusions weren't jumped to. 

So usual engineering principle - don't assume an engineering change can't have any impact, determine if it does have an impact and then find out why! Right down to root cause. Sadly too few audio companies seem to do the last step...but as said, both steps (can it be heard, and why) can be really really difficult.

What I've found interesting on audio forums in the past (I try to stay out of these discussions these days, bad for my blood pressure) is that these things work both ways, there are people who take it as a matter of deep belief and faith that certain things can't be heard. The ear-brain interface is pretty amazing at detecting differences, although the brain can be pretty rubbish at interpreting those differences. The biggest examples we found were that most people can tell the difference between two pieces of music with a 0.1dB level difference (although in our tests they didn't perceive it as a level difference), and that most people can hear absolute phase (at least on percussion type sounds). Both of which we found by accident, and at the times were, for different reasons, a pain in the bottom, we'd rather not have found them! I've had people rant and rave at me on forums when I've mentioned these, and try to find all sorts of bizarre explanations - much more complicated than the simple fact that they could be heard - which is interesting. I've always responded with "don't rant at me, go and try it". Of course there's also the question of whether either actually matter (which again is why I stay off such forums now), since you don't know which was "right" in the first place...ok, maybe there's a case for absolute phase in some cases. (They mattered to us because we were doing A-B comparisons and it was important that nothing unintended got in the way of these.)

I'll admit that one of the several reasons I left the audio industry was due to frustration with some of the uninformed discussions with clients - yes some of the capacitors in our systems are purple, no we don't consider that purple capacitors sound worse than blue capacitors, yes there is a make and model of capacitor that sounds worse than another make and model of capacitor but it's for these other technical reasons, not because it's purple...

These days I find musical instrument construction (as a hobby interest) much more interesting...but has many of the same issues, for example it's fascinating getting involved in the discussion of different varnishes on stringed instruments. (And again, some extremely well informed and researched, and some not...)

Sorry I was trying to avoid going off on my hobby horse but failed to stop myself! I'll shut up now.

Thanks,

Andy

And, although I am not from a hi fi background, (I'm the sort for whom you could make a simpler piano by eliminating every other key as they sound the same ...  musicians usually wince at this, but its true)  I am very much on your side - don't assume there will be  no perceived effect until you have measured everything well outside the 'normal' range.

Your comments about phase are interesting - do you mean phase of harmonics relative to fundamental (i.e, zero-crossing and peak moving), or just suck instead of blow by reversing the polarity of the coil of the speaker - which I'd expect to be discernible if the waveform is assymetric - which an N-wave event like an explosion usually is (- not too surprising - you can generate over pressure to many atmospheres at the origin of the explosion, but you cannot go below vacuum on the ensuing rarefaction. By the time you get far away, the pressures are less damaging, but the asymmetry is preserved. I can well imagine an upside down bang that starts with a suck instead of a blow sounding wrong.)

M.

mapj1 said:

or just suck instead of blow by reversing the polarity of the coil of the speaker

Yes exactly that. I don't know whether it's still true, but it certainly always used to be received wisdom that this couldn't be detected. My mentor in audio design (someone with a tremendous reputation, and with a fantastic set of ears) discovered it by chance when he was demonstrating an audio system which one day sounded different to him, and he discovered that someone had indeed reversed both sets of loudspeaker connections by accident. So we got quite interested, and set up an A/B test which we tried on absolutely anyone that passed - audio engineer or not!

As you say, it's not actually that surprising that, e.g., the initial hit on a bass drum sounds different depending whether it's "pushing" or "sucking" - particularly as we know the ear is non-linear. So it surprised me how emphatic some enthusiasts got that we must have biased the test somehow...

I was more impressed when a few years later we borrowed some fantastic people at the old BBC research centre to give us a second opinion on one of our designs, and one of them (again, someone rather well known back in the day for a certain loudspeaker design) picked up a very slight phase shift, over only a small frequency band, between our system and the reference...took us ages to find that one. He couldn't tell it what it was, but he could pick it out as "different" every time. The BBC research centre guys were really great to work with (my memory may be wrong, but I don't think we paid them anything, they just helped because they were interested), probably the most unbiased people I ever met in the industry..

Cheers,

Andy

I have long said that one of the great ironies in life is that by the time that you can afford the best audio equipment, you can no longer hear the difference.

(Yes, I do appreciate that there are a few v. wealthy young people.)

Actually, it's surprising. Even though we all lose our high frequencies (at the very least), there's lots of other aspects of hearing - I suspect particularly special positioning - that, providing we don't actually go deaf in one or the other ear, we do keep, and it does make a huge difference. As well as playing music I listen to a lot of live acoustic music, and the recorded version hardly ever actually sounds the same even with my 64 year old (and battered with loud music and power tool) ears. But I recently visited my 80 year old brother, who has possibly the best audiophile sound system I've ever heard (and as you'll gather I've heard rather a lot), who played a solo violin recording and it was extraordinary. With my eyes closed it did genuinely sound like they were there in front of me. (Of course it was also fantastically recorded which was why he was playing it to me.)

The ears themselves might deteriorate, but the brain can even improve it's ability to process sound over time given practice. On a related issue, by accident I've found myself helping fellow musicians of my sort of age move from playing from sheet music to playing by ear in sessions, which involves really working the way the brain processes sound. It's shown - and I know form my own experience - that it's amazing what you can learn to do in terms of processing sound. Which I guess is why it was promoted recently that one good way of delaying dementia etc is to learn a musical instrument late in life (makes me feel justified for having picked up three new ones in the last few years!) 

P.S. Not that I'd ever advocate spending huge amounts of money on a home sound system unless (like my brother and the OP) it's the thing you enjoy doing. When I was in the industry, and people asked my advice on buying hifi, I'd generally advise to just spend enough until you find a system that doesn't actively annoy you. Personally I probably could have afforded a reasonably expensive sound system at home long ago but all my money went on musical instruments instead...

Actually, it's surprising. Even though we all lose our high frequencies (at the very least), there's lots of other aspects of hearing - I suspect particularly special positioning - that, providing we don't actually go deaf in one or the other ear, we do keep, and it does make a huge difference. As well as playing music I listen to a lot of live acoustic music, and the recorded version hardly ever actually sounds the same even with my 64 year old (and battered with loud music and power tool) ears. But I recently visited my 80 year old brother, who has possibly the best audiophile sound system I've ever heard (and as you'll gather I've heard rather a lot), who played a solo violin recording and it was extraordinary. With my eyes closed it did genuinely sound like they were there in front of me. (Of course it was also fantastically recorded which was why he was playing it to me.)

The ears themselves might deteriorate, but the brain can even improve it's ability to process sound over time given practice. On a related issue, by accident I've found myself helping fellow musicians of my sort of age move from playing from sheet music to playing by ear in sessions, which involves really working the way the brain processes sound. It's shown - and I know form my own experience - that it's amazing what you can learn to do in terms of processing sound. Which I guess is why it was promoted recently that one good way of delaying dementia etc is to learn a musical instrument late in life (makes me feel justified for having picked up three new ones in the last few years!) 

P.S. Not that I'd ever advocate spending huge amounts of money on a home sound system unless (like my brother and the OP) it's the thing you enjoy doing. When I was in the industry, and people asked my advice on buying hifi, I'd generally advise to just spend enough until you find a system that doesn't actively annoy you. Personally I probably could have afforded a reasonably expensive sound system at home long ago but all my money went on musical instruments instead...

Andy Millar said:

.S. Not that I'd ever advocate spending huge amounts of money on a home sound system unless (like my brother and the OP) it's the thing you enjoy doing. When I was in the industry, and people asked my advice on buying hifi, I'd generally advise to just spend enough until you find a system that doesn't actively annoy you. Personally I probably could have afforded a reasonably expensive sound system at home long ago but all my money went on musical instruments instead...

So true. Most people can tell a really bad system, I can't listen to music on a mobile phone. When I couldn't really tell the difference between my Dual 505/NAD system and my flat mates Linn Sondek/Naim system (I'm dating myself here) however I stuck with the Dual (now replaced with a Denon system) and spent the money on my rally car.

Andy Millar said:

The ears themselves might deteriorate, but the brain can even improve it's ability to process sound over time given practice

To add to that, this is a great book I've just finished this book...

https://www.penguin.co.uk/books/442453/this-is-what-it-sounds-like-by-ogas-dr-susan-rogers-and-ogi/9781529114010

...that expands on what you said. Amongst other things, it explores what authenticity (in music) means to individuals.