I need to sync arpeggiator in my synthesizer with metronome sound (audio in). It does not need to be perfectly synced. Do you know it is possible to do such a patch like this. What object should I use to analyze incoming audio? Up till now I have been doing only midi patches, so audio in pd is quite new for me. I need to use only vanilla version because I'm going to use this patch on ipad (MobMuPlat). Can anybody help me??

@Llk998 Hello, [threshold~] will send a "bang" when its incoming audio signal exceeds a threshold that you can set.
Some vanilla objects are not available in mobmuplat though, and I cannot find the list.
If it doesn't work then try [env~] and feed its outlet to [> x] .....(x you will need to set to a "good" value, so that the data value "1" is passed on for every metronome click)...... and then the output of [> x] is sent to [select 1] which will output a bang every time the value x is exceeded.
You will probably get a series of bangs in rapid succession though. There will be a way to cope with that though. There is (almost) always a solution in Pd.
David.

@Llk998 in addition to what @whale-av has said, once you get a stream of bangs you can feed it into this tap tempo abstraction I once adapted from something somebody posted. The output is the averaged time between the last 7 bangs in milliseconds. It requires some list-abs abstractions which you can copy and paste elsewhere and are vanilla abstractions.

tap.tempo.pd