My ears (and brain) are being tricked and I just want to know how.

[Gilgamesh_48 943]

In the opening segment of Star Trek Voyager there is a section where visually the starship moves from behind the viewer to the front. But that is not really what I am asking about. at that time the sound actually sounds like it starts behind and moves to the front. I have tested with my eyes closed and the sound still moves back to front. What I want to know is how this is accomplished.

Let me tell you a bit about my audio setup:
I only have two speakers attached to my receiver and they are placed just a few feet from me exactly even with my ears.
The receiver is a simple Denon that is capable of advanced audio but is set to simple stereo.
My listening room is pretty acoustically dead or at least the acoustics are very weak.

The audio effect is quite startling and dramatic. I actually like it.

What I want to know is how such an effect could be produced with my setup. I understand how left to right or right to left can be produced as the speakers are directly right and left from my head. left to right and right to left or easy to understand but back to front is just hard to understand.

There are no other TV shows or movies that produce this effect.

This just for my info as it is not something I feel the need to "fix" and, yes, I understand that it may just be something I created in my own head but the effect is so dramatic that I do not think I am imagining it.

Thanks for any and all ideas.

Edited March 14, 2021 by Gilgamesh_48

[Guest]

Could be panning and pitch/frequency and room acoustics/materials...

TV producing sound as well?

Differences in speaker types ( Regular speakers vs. TV speakers ).. producing the same sound through the speakers - at the same time - when the frequency range of the sound itself changes and reaches the 'performance range' of the TV speakers it may actually be louder at the TV and lower through this range in the better speakers, I think I understood your speakers are behind or beside you.

Your AV may be doing this as well, or system attached producing video.. if there is a way the sound is being transferred. HDMI for example..

Acoustics and sound dynamics can be effected a easily by changing things in the room as well.. LOL. certain sound frequencies will reverberate off of surfaces and materials which absorb others.

Just a few guesses. I have kind of the same setup TV turned down.. but has options for it off..  nobody can figure out how it sounds like it does..  

[roaku 795]

I can't speak to the specifics of that scene, but my guess would be that the sound design went from bassy rumble then added more midrange information as the ship moved forward.

Low end information is harder for our brain/ears to localize.

Here's an article on the subject:

https://www.audiocheck.net/audiotests_basslocalization.php

There are many other mix effects available to simulate that kind of movement, but I think they're less likely to be used in a tv or movie mix.

Edited March 14, 2021 by roaku

[jachin99 82]

If your speakers are spaced just right ( they make an equalateral triangle with your listening position) then that's probably normal.  Look up stereo speaker positioning and you should see what I mean

[CharleyVarrick 277]

@Gilgamesh_48

As far as what you're hearing, isn't it the Doppler effect ?

https://en.wikipedia.org/wiki/Doppler_effect

 

Then there's brain "retentive association" for lack of better wording.

Don't look this up in google, just my attempt at naming this normal, food chain survival process.

Having seen many time the visual along with the sound, your brain remember the visual it associated to the sound, and "plays it" while you listen to the sound with eyes closed. Kind of when you hear a sudden car screeching full brakes on somewhere behind you, you dont have to see the source to get out of the way signal.

Edited March 14, 2021 by CharleyVarrick

[roaku 795]

In this case both the sound source and listener are stationary, so there is no Doppler effect.

[CharleyVarrick 277]

Doppler is basically varying pitch and varying intensity at once.

Just one or the other doesn't give the info to the brain.

Once recorded, why would a  loudspeaker not be able to reproduce it?

 

Granted, a 5.1 system carefully calibrated (audio delay) would augment the realism effect to the point you'd think the spaceship actually entered your living room.

 

Not totally related but high pitch sound travels like a light beam while bass goes out in all direction at once.

Tweeter works best at ear level, while your sub woofer could be in the next room.

Edited March 14, 2021 by CharleyVarrick

[Guest]

True.. wavelength and impedance..

Edited March 14, 2021 by Guest

[roaku 795]

Because there is no spaceship and no one in a space suit with a field mic and if there were, they both would have been in space at the time and therefore no medium for the sound to travel through and no Doppler effect to experience.

This is sound design and mixing.

From the opening of your Wikipedia link:

"The Doppler effect (or the Doppler shift) is the change in frequency of a wave in relation to an observer who is moving relative to the wave source."

 

Edited March 14, 2021 by roaku

[CharleyVarrick 277]

Sound wave do need air to travel, and by the way the spaceship is CGI.

OP example could have been a tractor trailer passing by camera and mics on the highway. Same exact deal.

If you imagine that scene with eyes closed it would also give limited effect of movement.

Having seen it at least once would introduce a new back to front axis to basic left and right stereo.

Edited March 14, 2021 by CharleyVarrick

[Guest]

No, no I swear I was there just like that.. nothing but silk boxers and a spacesuit... Listening to Spaceman... so out of my mind just waiting for the next ship to record.. 

I think its both and brain expectency.. sound has some capabilities that are not direct.

[roaku 795]

Just now, CharleyVarrick said:

Sound wave do need air to travel, and by the way the spaceship is CGI.

OP example could have been a tractor trailer passing you by on the highway.

The sound designers could certainly go out and set up a field recording of a subject and capture a Doppler effect and on playback, you would hear the frequency shift and if they used multiple mics, could even capture the sound's movement across a stereo field, but this would come with a ton of practical and technical limitations both in the design and dubbing stages, so they wouldn't do that.

They would instead capture their sound sources as stationary as possible, so they can easily add in other sources and then recreate whatever motions the fake spaceship simulates in this and future episodes with effects and mixing technique.

[CharleyVarrick 277]

Back to OP's example.

Simple physical setup, a tv with actual stereo speaker (not just L&R speakers playing same exact thing)

Take a blind person that has never seen the spaceship animation coming from behind and moving past to the front. (no audio description enabled or someone describing the scene to him).

 

That person will get increasing/decreasing distance info (doppler effect), and might also experience left to right information, if applicable.

But no realist back to front info can come out of a pair of speakers if they're positioned in front of the subject.

For that, it would require satellite back speakers plus well tuned surround effect.

 

In the OP's example, his brain just remembers what it saws and "plays the picture" inside the brain. Eyes are just component for vision, an important part, mind you, but 10% of your brain mass is reserved to process the visual info.  Imagine a camera lens without a camera attached to it, and without film or memory card to record.

 

A blind person does "see" things in his brain, when blindness happens after accident or disease, the brain remember (more or less) how things used to look before.

Blind at birth people still see things in their brain, but without actual frame of reference, so "green" is a non information to them.

 

In closing most people do not know this, but our eyes, just like any camera lens, produce an inverted top down image. The brain process the received image to bring it back correctly. 

I was reminded of this when I recently used an ext webcam on my desktop pc. Something's wrong I thought.

We are all used to look at ourselve in a mirror, but that too gives us an inverted image. Hence Your left vs My left

 

 

 

Edited March 14, 2021 by CharleyVarrick

[pwhodges 1532]

This front/back localisation is partly learned - we learn as infants to associate the subtlest audio clues to specified occurrences in the real world. 

We have but two ears, and still find ways to localise all around.  One mechanism involves head movement, which reduces ambiguity, but another uses subtle changes in tonality caused by filtering which comes from the pinnae, and from shoulder reflections.  These are highly personal, but can be measured (it's called HRTF - head-related transfer function) and applied to sounds from different directions in processing for binaural (headphone) listening.

It is possible to use an average HRTF for a less certain result, which works better for some people than others, and it's possible to fudge some of its effects into loudspeaker listening.  If it works for you, great - but don't be surprised if the results are poor or variable.

Paul

[roaku 795]

Again, manipulating the eq of the sound to move from low frequency heavy to more mid range and high frequency creates a sense of back to front motion in the soundscape for a listener in a stereo environment.

There are more techniques available, most which are less likely to be used for a TV or movie mix.

 

Here's a good thread with advice on how to achieve the effect in stereo:

https://sound.stackexchange.com/questions/8540/sound-coming-from-behind-using-stereo-field

[CharleyVarrick 277]

27 minutes ago, pwhodges said:

This front/back localisation is partly learned - we learn as infants to associate the subtlest audio clues to specified occurrences in the real world. 

We have but two ears, and still find ways to localise all around.  One mechanism involves head movement, which reduces ambiguity, but another uses subtle changes in tonality caused by filtering which comes from the pinnae, and from shoulder reflections.  These are highly personal, but can be measured (it's called HRTF - head-related transfer function) and applied to sounds from different directions in processing for binaural (headphone) listening.

It is possible to use an average HRTF for a less certain result, which works better for some people than others, and it's possible to fudge some of its effects into loudspeaker listening.  If it works for you, great - but don't be surprised if the results are poor or variable.

Paul

I remember 40 years ago or so experiencing a ultra high end stereo system demo in a store. Salesman asked I close my eyes to listen to classical percussion ensemble (recorded with the mics inside a dummy head).

 

He then asked what my impressions were and I described exactly where all the different instruments were in the room. He just smiled and said "you got this!" 

[CharleyVarrick 277]

1 hour ago, pwhodges said:

This front/back localisation is partly learned - we learn as infants to associate the subtlest audio clues to specified occurrences in the real world. 

We have but two ears, and still find ways to localise all around.  One mechanism involves head movement, which reduces ambiguity, but another uses subtle changes in tonality caused by filtering which comes from the pinnae, and from shoulder reflections.  These are highly personal, but can be measured (it's called HRTF - head-related transfer function) and applied to sounds from different directions in processing for binaural (headphone) listening.

It is possible to use an average HRTF for a less certain result, which works better for some people than others, and it's possible to fudge some of its effects into loudspeaker listening.  If it works for you, great - but don't be surprised if the results are poor or variable.

Paul

I had to reread your post to fully get what you were saying.  3d sound from one's 2 ears in the real world ie: standing in middle in a room. That I agree 100%, as again our hearing is more than just ears, again a significant portion of our brain is dedicated to processing sounds.

 

Where I have big doubt is getting 3d sound coming out of a pair of speakers in front of you. That would require pretty fancy equipment (costing 100x more than a 5.1 well tuned system), and would likely be a pale imitation at best.

Edited March 14, 2021 by CharleyVarrick

[CharleyVarrick 277]

2 hours ago, roaku said:

From the opening of your Wikipedia link:

"The Doppler effect (or the Doppler shift) is the change in frequency of a wave in relation to an observer who is moving relative to the wave source."

 

That explains indeed how the effect is observed.

 

My point is once the effect is achieved, its child's play to record it and reproduce the effect, using a mere single 2 " speaker.

You will hear the approaching/receding effect, but no sense of direction, obviously.

 

Say you're talking on the phone with a friend. During the call, a firetruck with blazing siren approaches your friend's location, passes by and drives away.

Even thru your phone tiny single speaker, you will experience the doppler effect observed by your friend and caught by his phone mic and sent to you phone speaker.

 

I rest my case.

Edited March 14, 2021 by CharleyVarrick

[roaku 795]

31 minutes ago, CharleyVarrick said:

That explains indeed how the effect is observed.

 

My point is once the effect is achieved, its child's play to record it and reproduce the effect, using a mere single 2 " speaker.

You will hear the approaching/receding effect, but no sense of direction, obviously.

As I said, it's easy enough to record the Doppler effect in the field. 

 That doesn't make it useful or practical for most sound design scenarios precisely *because* you've captured context specific information from the field that limit your options when you do the mix.

Think about how all bullets in TV shows from the '50s and '60s ricochet with a long reverb tail even if it's a Western in the middle of a desert, or think about how they intentionally recreated those outdated techniques and used actual old library recordings (Wilhelm scream and others) for the Indiana Jones movies.

A '90s spaceship that reappears throughout a TV show is going to be made up a bunch of sounds, some real, some synthetic, that need to be combined to sound like one source and that combined source needs to be able to be mixed in different ways to quickly recreate the visual cues of the ship's on screen movements from episode to episode as well as fit in with the sound palette of everything else in the show.

The last thing you want in your source recordings is things like Doppler, environmental reverb, and amplitude shift from the sources movements. Those are the reasons you would throw out that source recording and try something else.

 

 

Edited March 14, 2021 by roaku

[CharleyVarrick 277]

4 hours ago, roaku said:

In this case both the sound source and listener are stationary, so there is no Doppler effect.

You also said this, which, in itself in the context of the OP question is false and "sparked" the debate.

Lets move on, shall we?

Edited March 14, 2021 by CharleyVarrick

[roaku 795]

Here's the sound mixer on Voyager describing how he used mix techniques to create ship movements using the sound effects the sound designer provided him.

Again, this was only possible because the sound designer knew better than to imprint movement and environmental reverb that would make the mixer's job next to impossible.

"'I also have four automated pan pots--each up to 8 channels--and I rely on them quite heavily for ship-by effects, and effects that are moving overhead, and from front to back on-screen. I use them extensively, and I can still maintain the stereo integrity of the effects and get a nice, smooth even pan..."

http://www.filmsound.org/studiosound/pp_startrek.html

 

[roaku 795]

10 minutes ago, CharleyVarrick said:

You also said this, which in itself is false and "sparked" the debate.

Lets move on, shall we?

There still is no Doppler effect there.

That's like saying that if a filmmaker points his camera at the sun, his movie will blind you.

No, an event was recorded at a moment in time. Playing that event back from a recording is not that moment in time.

The sound waves being recreated by the speaker are not the originals. The source of the original sound is not in your room.

The speakers and the listener are not moving relative to each other. There is no Doppler effect.

Edited March 14, 2021 by roaku

[ebr 14924]

For the layperson - the way your brain "localizes" the source of a sound has to do with the frequency response of the human ear.  When things come from behind you, the ear itself causes frequency changes in the source sound.  Then, also, there is the difference in time between the sound hitting one ear or the other.  Combining these things enables your brain to interpret a direction for the source.

Simulated surround sound (and stereo, for that matter) uses these techniques to trick your brain into thinking sounds are coming from wherever they want.

[CharleyVarrick 277]

15 minutes ago, roaku said:

There still is no Doppler effect there.

That's like saying that if a filmmaker points his camera at the sun, his movie will blind you.

No, an event was recorded at a moment in time. Playing that event back from a recording is not that moment in time.

The sound waves being recreated by the speaker are not the originals. The source of the original sound is not in your room.

The speakers and the listener are not moving relative to each other. There is no Doppler effect.

With that unique reasoning of yours, next time you watch anything on tv, don't forget to remind yourself that what comes out of your TV speakers and reaches your ears is not sound, as after all, you and your tv were not present in the studio at the time of recording.    

[roaku 795]

Just now, CharleyVarrick said:

With that unique reasoning of yours, next time you watch anything on tv, don't forget to remind yourself that what comes out of your TV speakers and reaches your ears is not sound, as after all, you and your tv were not present in the studio at the time of recording.    

You're choosing not to hear anything, but maybe others are listening.