Hertz
The hertz (or Hz) was a unit of frequency, where one hertz was equal to one cycle per second, used to describe ranges of sound, of the electromagnetic spectrum, and of brain waves.

Used in applications 
Decihertz (10−1 Hz, dHz)
 0.3 decihertz: In 2376, Seven of Nine told The Doctor he was off-key in the third verse, second measure of the song "My Darling Clementine". The Doctor said that was impossible, but she verified her comment, stating that his vocal modulations deviated by 0.30 decihertz, which she offered to assist him to correct the next day in the Holodeck. He agreed, offering to also bring a tuning fork. ()

Hertz
 1 Hz and 100,000 THz: Geordi La Forge's VISOR operating frequencies were between 1 Hz and 100,000 THz. ()
 4 to 7 hertz: The frequency range of 's theta wave as recorded by her atomic scan in 3189. ()
 5 to 15 hertz: The EM pattern given off by the Sentry on one of the moons in the Pentarus system remained between 5 and 15 hertz when the water fountain it protected was not threatened. ()
 8 to 12 hertz: The frequency range of Philippa Georgiou's alpha rhythm as recorded by her atomic scan in 3189. ()
 17 to 29 hertz: The frequency range of Philippa Georgiou's beta wave as recorded by her atomic scan in 3189. ()
 40 hertz: When the fountain was approached, the Sentry's frequency would rise to 40 hertz. ()
 880 hertz: In 2375, The Doctor sang up to a range of 880 hertz in order to check for damage to Chakotay's auditory nerves. This was done after exposure to chaotic space had reactivated a previously suppressed gene that caused, among other symptoms, auditory hallucinations. ()
 2.43 × 1022 hertz: A gamma scan conducted by the crew of the Enterprise-D in 2368 had a composite frequency of 2.43 × 1022 hertz (24.3 billion terahertz). ()

Kilohertz (103 Hz, kHz)
 0.3 kilohertz: In Reginald Barclay's simulated attempted to contact , he had the transceiver gain set to maximum, then applied a narrowband filter to the signal processor, before lower the filter band by 0.3 kilohertz. When finally implemented in real, he was able to finally make contact with Voyager. ()
 5.75 kilohertz: Frequency for radio wave JAG 3802725A emitted by a neutron star near the Verubin Nebula. ()
 340 kilohertz: The high-energy disruptor weaponry used by Cardassian warships in 2367 had an estimated coherent output of 700 megawatts and a 340 kHz rapid nadion effect. ( display graphics) 

Megahertz (106 Hz, MHz)
When the  used a microprobe as a subspace communications relay to contact a Romulan science vessel through a micro-wormhole, B'Elanna Torres noted that the phase amplitude of the visual link with the ship was within a few megahertz of transporter protocols. ()

 10 to 100 megahertz: ()
 15 megahertz: Arik Soong had  adjust its scanning frequency to 15 megahertz to located the Augments stolen . ()
 15 megahertz: While manually conducting a lateral scan aboard the disabled , Major Kira noted that the sensors were set at 15 megahertz for their range of five hundred kilometers. ()

 257.4 megahertz: The frequency modulation for the shields of , prior to its destruction in 2371, was 257.4 megahertz. When the Duras sisters discovered this frequency, they adjusted the frequency of their weapons, allowing them to directly impact the Enterprises hull. ()
 401 megahertz: George and Gracie were tagged with the radio frequency was 401 megahertz prior to their journey from the Cetacean Institute to their release into the wild. ()
 1 million megahertz: The frequency of the message transmitted by V'ger was sent at a rate of one million megahertz (1 terahertz) and lasted only a millisecond. At that high rate of speed, the message was initially undetected. ()

Gigahertz (109 Hz, GHz)
 1.85 gigahertz: Hand phasers set to a dispersal frequency of 1.85 gigahertz were able to penetrate the Voth cloaking technology. ()
 4.84 gigahertz: Subspace warheads encounter by Voyager in 2377 had an activation frequency of 4.84 gigahertz. ()
 12 gigahertz: In 2372, the Voyager crew established contact with their duplicates by sending them a brief message telling them to lock onto a frequency of 12 gigahertz. ()

 92 gigahertz: In 2373, the swarm hit Voyager with a polaron burst that changed the deflector shield polarity, causing it to rotate at 92 gigahertz. ()
 97 gigahertz: By increasing the warp plasma 97 gigahertz, Miles O'Brien could increase the velocity of the USS Defiant to warp 9.5. ()
 384.20 gigahertz: The subspace communications frequency utilized in Earth Starfleet communications was 384.20 gigahertz. ()

Terahertz (1012 Hz, THz)
Three hundred twenty-seven systems that used terahertz feeds were known to the Federation in 2367, none of which were used by Starfleet. The forged Federation phaser rifles created by the Romulans, discovered on Krios Prime and used by Kriosian rebels, were charged with a forced pulse, well into the terahertz range. This range is similar with those found in Romulan disruptors, which create an inverted initial output spike, with corresponding discharge crystal and emission beam pattern. ()

 0.06 terahertz: The attack by Voyager on Tactical Cube 138 in 2376 created a 0.06 terahertz fluctuation in the cube's ventral shield grid, enough to allow a team aboard the  to beam aboard. ()
 0.47 terahertz: In 2374, during an attempt to beam deuterium from beneath a class Y planet's surface, Voyagers transporter's annular confinement beam was narrowed to 0.47 terahertz. ()
 1.68 terahertz: ()
 7 terahertz: ()
 8.6 te[t]rahertz: ()
 400 to 850 terahertz: In the mirror universe, in the 2250s, the bridge primary dorsal sensor array of the  had an electromagnetic frequency of 400 to 850 THz. ()

External link

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Measurements
Mirror universe