How to make sure iOS Audio Hardware Decode worked?

I've created an iOS project that plays music file looped. I configured the audio file to "Compressed(MP3)" and "Stream from disc". Then I checked the "Hardware decode", and deploy the project to my iPad 1.

I know iOS can only play one audio by hardware decode at a time, so I close all other applications on my iPad1 and make only 1 sound file enable "Hardware decode" in my project.

I opened profiler and found that no matter "Hardware decode" is checked or not, the audio area of profiler shows that audio uses about 5%~6% cpu (streaming cpu). Is it normal or I just didn't really enable "Hardware decode"?