Anyone with an Android smartphone should be able to download an audio
   spectrum analyzer app to detect various sonic events.
   Further, I believe that USB-connected  SDR's (Software-Defined Radios)
   which can implement cheap spectrum analyzers are cheaply available.
   [1]https://www.walmart.com/ip/100KHz-1-7GHz-Full-Band-UV-HF-RTL-SDR-USB
   -Tuner-Receiver-DIY-Kits-U-V-Antenna/199714416?wmlspartner=wlpa&selecte
   dSellerId=101003580&adid=22222222227288811307&wl0=&wl1=g&wl2=c&wl3=3468
   28962873&wl4=pla-735633419885&wl5=9061079&wl6=&wl7=&wl8=&wl9=pla&wl10=1
   33212149&wl11=online&wl12=199714416&wl13=&veh=sem&gclid=CjwKCAjwwtTmBRB
   qEiwA-b6c_w-ZuOpEfxEMZEimG4CIU2EsgC9O5wjNx0OPs5kj_0jI-f1bA3TJQ8hoCwCAQA
   vD_BwE
   $25.31, in kit form.
   Although, this specific one is limited to 100Khz-1 GHz.
   Anything reasonably usable to go to at least 3 GHz.
                      Jim Bell

   BY BOB SALSBERG, Associated Press

   BOSTON (AP) — A U.S. diplomat who said he suffered headaches and memory
   loss under mysterious circumstances while stationed in China pledged
   Friday to donate his brain to head injury researchers.

   Mark Lenzi, 44, is an unusual addition to the several thousand others,
   including many former NFL players who suffered concussions during their
   careers, who previously signed agreements to have their brains studied
   after they die by the CTE Center at Boston University.

   A security engineer for the U.S. State Department, Lenzi was among a
   number of diplomats who were brought home last year from the U.S.
   Consulate in Guangzhou, China, after reporting as-yet-unexplained
   symptoms.

   The State Department has drawn no link between those diplomats and 26
   workers at the U.S. Embassy in Cuba who were withdrawn in 2017 after
   reporting symptoms, including those consistent with minor traumatic
   brain injury, or concussion.

   "The engineer in me wants to get to the bottom of this type of
   concussion and exactly what happened to me," Lenzi said while signing
   the pledge in Boston with representatives of the Concussion Legacy
   Foundation, an organization that collaborates with the BU researchers
   by recruiting donors and publicizing the dangers associated with head
   trauma.

   Chris Nowinski, co-founder and chief executive of the foundation, said
   the brain injury community must continue research to find answers for
   head trauma.

   "There are patients out there that need answers from the scientific
   community," he said.

   Lenzi now works at a State Department passport office in his native New
   Hampshire. He said he and his wife began hearing strange noises in
   their apartment in 2017, and later developed symptoms consistent with
   concussion. In an interview with the AP, he said he initially did not
   associate the noises with the symptoms, believing the headaches may
   have been triggered by smog.

   Lenzi has not been identified by U.S. officials as someone suffering
   from injuries similar to those suffered by diplomats in Cuba.
   The State Department said Friday that out of 15 diplomats or family
   members from China who underwent additional medical evaluation in the
   U.S., 14 were found not to have symptoms like those from Cuba and the
   other case had not been determined.
   [end of partial quote]

References

   1. https://www.walmart.com/ip/100KHz-1-7GHz-Full-Band-UV-HF-RTL-SDR-USB-Tuner-Receiver-DIY-Kits-U-V-Antenna/199714416?wmlspartner=wlpa&selectedSellerId=101003580&adid=22222222227288811307&wl0=&wl1=g&wl2=c&wl3=346828962873&wl4=pla-735633419885&wl5=9061079&wl6=&wl7=&wl8=&wl9=pla&wl10=133212149&wl11=online&wl12=199714416&wl13=&veh=sem&gclid=CjwKCAjwwtTmBRBqEiwA-b6c_w-ZuOpEfxEMZEimG4CIU2EsgC9O5wjNx0OPs5kj_0jIf1bA3TJQ8hoCwCAQAvD_BwE