Is Acoustic Wave therapy effective for ED?

To answer your question with the most straightforward language you have first to understand the reason for the ED. Penile erection is a physiological process that consists of blood circulation and muscle strengthening. As aging happens, blood vessels shrink, plaques inside blood vessels which is also called atherosclerosis of blood vessels (secondary to high cholesterol, sugar, smoking, etc.) reduces blood circulation causes erectile dysfunction.
Shockwave treatments throw powerful shockwaves which are few centimeters in depth and can break down plaques inside blood vessels, increase blood circulation, and help with muscle strengthening. Each treatment is consists of applying around 3-5K joules of energy. This treatment can be combine with the famous PRP treatment called P-Shot and increase the efficassy of the results. You will need minimum 8-10 treatments(normally done twice a week) to see some improvement. I hope I have answered your question.

Using Acoustic Wave therapy to treat ED has been well studied and found to be completely safe, with no known side effects - and effective.  Please see a link to one recent article, below.
In general, Acoustic Wave therapy works by improving blood flow to the penis.  Better blood flow results in erections that are easier to achieve and sustain; results last 2 years or so.  After that time, men will often pursue a maintenance treatment once every year or so as needed, if / when they begin to notice the problem beginning to recur.
Unlike medications or injections which are designed to create an erection in the moment, but do not do anything to address the underlying problem, Acoustic Wave therapy actually creates a beneficial physiological change, the growth of new blood vessels, that provides lasting benefits. 
The specific treatment protocol that will give you optimal results depends on the severity of the problem. Men who have mild ED and don't have any other medical conditions; don't take medications; don't smoke, can often do well with 4 - 6 Acoustic Wave treatments.  For men with more more factors contributing to erectile functioning difficulties, we find that more treatments may be necessary, and combing Acoustic Wave therapy with P Shots can be more effective than either treatment alone. 
It is also recommended that you use a pump twice daily for at least 8 weeks following the Acoustic Wave and or P Shot treatments, to optimize results.  The pump brings blood flow to the area which accelerates the healing response.