4ch

• Sennheiser AMBEO VR Mic
• Soundfield ST450 mk2 http://www.soundfield.com/products/st450mk2
• Schoeps http://www.schoeps.de/en/products/ortf-surround-bar
• SPS200 Zephyx kit - 4ch soundfield mic

Telinga parabolic reflectors

• http://www.telinga.com/products/
• e.g. http://www.telinga.com/products/pro-series/microphones/parabolic/stereo-mk2/

hydrophones

• Aquarian H2a-XLR Hydrophone http://www.aquarianaudio.com/h2a-xlr-hydrophone.html

ambisonics

• ambiX v0.2.7 – Ambisonic plug-in suite http://www.matthiaskronlachner.com/?p=2015
• richard devine http://www.creativefieldrecording.com/2017/03/14/explorers-of-ambisonics-richard-devine/
• anna bertmark http://www.creativefieldrecording.com/2017/03/16/explorers-of-ambisonics-anna-bertmark/
• https://endabates.wordpress.com/2017/06/19/comparing-ambisonic-microphones/

notes

• Microphones for nature recording https://www.wildmountainechoes.com/equipment/microphones-nature-recording-ii-different-microphones-different-situations/

ultrasonics

• using a mobile or ipad > https://www.wildlifeacoustics.com/products/echo-meter-touch-2
• https://www.wildmountainechoes.com/equipment/options-for-recording-ultrasounds/
• http://www.avisoft.com/usg/microphones.htm

• comparison of sony microphones http://infos.0db.net/micros/compare/indexe.php3
• in-ear binaural microphones http://www.soundprofessionals.com/cgi-bin/gold/category.cgi?category=search&item=SP-TFB-2&type=store