Sound 'Phasing' - Is it still a thing?

[Ian J.]

Hi all,

 

Please excuse the dullness of this question, I don't currently have much in the way of sound equipped locomotives, or a layout to run them on and I'm only just beginning to build up a sound-fitted fleet very slowly.

 

I seem to remember a long while back that when having two locomotives with the same sound project running on a layout at the same time, there would be 'phasing' in the sound due to the exact same sounds playing out of sync. Is that still a thing? If so, other than trying to make sure all locomotives have different sound projects in them, how can this be overcome?

 

My thoughts here particularly turn to situations where two locomotives of the same class are either double heading / top-tailing, or are in close proximity to each other on a layout, e.g., two class 20s on a weed-killing train.

 

TIA

Edited June 25, 2022 by Ian J.

[Hroth]

Its a phenomenon in the real world.   Not so prevalent nowadays but prop-driven planes with internal combustion engines would make a warbling drone if the engines weren't synchronised, pilots would be skilled in juggling the throttles to even the effect out. It was highly noticable and not a good thing to be doing when on a bombing run...  

 

Its probably a thing with any two or more closely coupled engines running at a constant speed, but not as noticable nowadays.  I don't know how you would overcome it with sound equipped locomotives but its probably prototypical!

[Ian J.]

I think the problem I have is that the recorded sounds have a more 'artificial' sound to the phasing, where in real life, not only does it not sound so 'artificial' but the differences between the locomotives' wear and tear means they don't phase anything like as much.

 

I think the different projects route might be the only solution. That means not buying multiple locos with the same sound fitting (i.e. all from the same manufacturer), but making sure that additional locos aren't bought with sound, and then getting after-market decoders with known 'unique' sound projects for any given class.

[Hamburger]

This is a known issue. Phasing occurs when both sounds are the same, but are played very, very slightly differently.
I can only think of a solution for ESU V4 and V5, because you can easily pitch the engine sound there using CVs.
3% up or down on one of the two locomotives is usually enough to achieve an attractive result.
I suspect Legomanbiffo does the same for double loco projects.

[F-UnitMad]

21 hours ago, Hroth said:

Its a phenomenon in the real world.   Not so prevalent nowadays but prop-driven planes with internal combustion engines would make a warbling drone if the engines weren't synchronised, pilots would be skilled in juggling the throttles to even the effect out. It was highly noticable and not a good thing to be doing when on a bombing run...  

As made famous by the Luftwaffe in WW2, who didn't synchronise their bomber's engines, so there was a distinct 'throbbing' sound to them. Also led to the phrase "It's ok, it's one of ours." when RAF planes were up & about - people didn't need to look up to check. ;)

 

No idea what the solution is for DCC model locos, though. I did have the issue when I had a couple of identical HO locos, but nowadays in O I don't have any identical sound-fitted ones.

[RAF96]

I thought phasing was getting all the speakers in a Hi-Fi system to push and pull together, by making sure all the speaker positives were connected together and all the negatives together (woofer, mid-range and tweeter).

What we seem to be talking about here is beat frequency where one sound system is off frequency to the other sŷstem and every time the two match you get a beat, in the case of aircraft engines a throbbing that irritates after a while. The phenomenon was used in radios called heterodyning where one frequency beats against another and the matching beats lock on at that new frequency.

[SHMD]

I seem to recall Deltic's doing this when setting off from stations - even better if you were right behind the loco.

 

 

Kev.

 

[Ian J.]

11 hours ago, RAF96 said:

I thought phasing was getting all the speakers in a Hi-Fi system to push and pull together, by making sure all the speaker positives were connected together and all the negatives together (woofer, mid-range and tweeter).

What we seem to be talking about here is beat frequency where one sound system is off frequency to the other sŷstem and every time the two match you get a beat, in the case of aircraft engines a throbbing that irritates after a while. The phenomenon was used in radios called heterodyning where one frequency beats against another and the matching beats lock on at that new frequency.

 

I used the term 'phasing' as I don't know what else to call it and that's kind of what it sounds like. I did use quotes around it as I know it's probably not the right term.

[Erixtar1992]

Adjusting the min\max sound slot speed a couple percent helps this a lot

[Pete the Elaner]

12 hours ago, Ian J. said:

 

I used the term 'phasing' as I don't know what else to call it and that's kind of what it sounds like. I did use quotes around it as I know it's probably not the right term.

 

I remember being taught about this at school. I think the term used was 'booming' but it was a long time ago.

 

It explains some music theory too, although I get told I overthink it. The "same note" an octave higher is exactly double the frequency, so their waveforms are in sync often (every cycle for the lower note) which is what makes them sound nice together. What does this have to do with the effect being described? 2 notes close to each other, for example A & A#, sound quite uncomfortable because their waveforms are not in sync very often.