Troubleshooting

Microphone Input Connection for iPhone

We ran into a few problems when attempting to collect data using the hydrophone.  We attempted to connect the hydrophone to our iPhone using several different adapters and have yet to find a compatible input connection so that the app NIOSH will recognize our external microphone.  It is important to collect the data only from our hydrophone, otherwise you will collect data around you using your internal microphone on your iPhone instead of data under the water. 

We think we have found the problem. We are currently looking for a splitter with a microphone input connection that is compatible with iPhones.  The NIOSH app is only built for apple devices.  Therefore you need a product with a TRRS or 4 conductor wiring configuration (something that only apple uses and recognizes).  We also read we need a CTIA  instead of an OMTP wiring configuration.  We wrote the developers of the NIOSH app at EA LAB, and they confirmed that we have yet to find the correct adapter.

We have tried several options that did not work.

Lightning to Headphone Jack: This option only changes the connection from a 3.5 mm headphone jack to a lightning connector

iRig Pre HD: This option allowed us to use the hydrophone as a microphone and record sound on our iPhones.  Unfortunately, the NIOSH app did not recognize it as an external microphone.

Splitters: We also have tried two splitter options.  One of them was OMTP.  Another, we thought would work, but we did not read the fine print.  It stated it was compatible with iPhones and it was CTIA, but I later saw it also said not TRRS.  One of the issues we ran across is these types of splitters are not sold in stores including Best Buy.  

Accurate Decibel Levels

Another question we have concerning collecting data using the NIOSH app and the hydrophone is, will we able able to get an accurate decibel level?

We are not sure how the microphone will accurately receive the decibels levels and transmit them to the phone because the sound that the microphone picks up is always quieter than the actual sound.  We also learned that some homemade hydrophones work better than other.  Would different hydrophones give you different decibels levels?  When researching our microphone input connection and the NIOSH app, we read articles on how important it is to have a good quality, calibrated microphone.  

Quality of Materials is Important:

Our second hydrophone had much better sound quality.  It may have been due to building experience, so if you are not happy with the first one try again.  We also changed the place we ordered the stereo cord and Piezo Element from.  Due to a shipping issue, we ordered our first Piezo Element and stereo cord off of Amazon.  For the second one, we ordered the Piezo Element from SparkFun and the stereo cord from McMaster-Carr.  It seems to us that the tricky part is adding the epoxy at the end.  Before adding the epoxy, you test out the hydrophone and we noticed a difference in sound right away.  This was confirmed when we tested both hydrophones out next to the bike ferry in Menemsha.