Position of speaker in front of tube to produce stationary wave

[songoku]

That is part of the article. I want to ask about step 4. I know the basic theory of how stationary wave is formed (superposition of incoming and reflected wave) and also basic concept about stationary wave in open and closed tube, something like this:

But I don't know the reason why in step 4, the speaker must be placed at angle 45^o, not pointed directly into it. If I imagine it, putting the speaker directly in front of the tube will also produce reflection and possibly stationary wave.

Why should be the speaker placed at certain angle? And must it be 45^o, or can it be some other angle such as 60^o?

Thanks

 

[sophiecentaur]

Summary:: I googled a lot of thing related to experiment to produce stationary wave using speaker and open / closed pipe and I saw an article.

Why should be the speaker placed at certain angle? And must it be 45o, or can it be some other angle such as 60o?

I think it must be to reduce the 'coupling' of the loudspeaker diaphragm to the wave in the tube and so that the reflection of the exiting wave will tend to be deflected away from the tube and not back into the tube and present an 'almost closed' end to that wave, affecting the resonance. The angle won't be ever so critical.

 

[songoku]

I think it must be to reduce the 'coupling' of the loudspeaker diaphragm to the wave in the tube and so that the reflection of the exiting wave will tend to be deflected away from the tube and not back into the tube and present an 'almost closed' end to that wave, affecting the resonance. The angle won't be ever so critical.

Thank you very much sophiecentaur