sound stimuli needs to have ramp up

[mz973]

currently onset clicking, needs to be smoother

[am4002]

psychopy apperently does put an evelope on all the sounds it generates by default - so the clipping is (probably? hopefully?) because of a low bitrate/low buffer size. Increased size both of them (bits 8 > 32, buffer 128 > 4069), leaving this open because I'm not sure it's made enough of a difference