We can't hear anything at upacāra of first jhāna, and go on.
1) Pañcadvārāvajjana is very sensitive with bhavaṅga, because bhavaṅga can be Pañcadvārāvajjana's ārammaṇa-anantara-nissaya-ūpanissaya-purejāta-natthi-viggatapaccayas--let-able Pañcadvārāvajjana arise after it without separate, so Pañcadvārāvajjana can arise in khanikasamādhi.
But pañcadvārāvajjana can't arise after jhānacitta without seperate, many types of citta must arise after jhānacitta and before it because jhānacitta can be only upanissaya-natthi-viggatapaccaya. It's so far from 5 kāmagunas.
Upacāra of anyjhāna still sensitive more than appanājhāna. It must drop to bhavaṅga every 7 arisings, so it identify about lower power of it that can't win bhavaṅga. However it narrowly win akusala, and its concentrating nimitta more power than khanika, so 5 kāmagunas can't access upacārasamādhi while it go on, too.
2) 5 vatthus are kammajarūpa and indriyapaccaya, so observing them from kamma's vipāka are harder than hatayavatthu of jhānacitta that's only kammajarūpa but it isn't intriyapaccaya.
3) Citta can arise only one per time. So if jhāna is "strong exertion to direct one's mind to do something" or "ekaggatā", it couldn't sense anything by 5 senses because they are out of onemind and out of one thing.
This commentary passage is refer to senseless by 5 senses, except 6th sense, of samatha-developer.
Somanassañhi catutthajjhānassa upacārakkhaṇeyeva pahīyati, dukkhadomanassasukhāni paṭhamadutiyatatiyajjhānānaṃ upacārakkhaṇesu.
Mind-sukkha begins to pause at upacāra-samādhi of 4th jhāna. Physical-dukkha, mind-dukkha, and physical-sukkha begin to pause at upacāra-samādhi of 1st, 2nd, and 3rd jhāna.
Just a conclusion, see at link for more information: http://tipitaka.org/romn/cscd/s0515a.att2.xml#M0.012
P.S. Sleeper, and dis-attended body don't hear the sound, too. So hearing isn't importance to decide jhāna. Tipitaka and ommentary emphasize to know about mind elements more than it. Sound hearing just be suppāya that we should prepare to deny before meditate.
Attend lakkhaṇādicatukkas to understand mind state more to develop it.