Acoustic microscopy acoustic microscope (CSAM), and C-mode scanning acoustic microscope (C-SAM). More recently acoustic microscopes based around picosecond ultrasonics systems have demonstrated acoustic imaging in cells using sub-optical wavelengths working with ultrasonic frequencies into the multi-GHz. Since the vast majority of acoustic microscopes in use today are C-SAM type instruments, this discussion will be limited to these instruments. Ultrasound is broadly defined as any sound having a frequency above 20 kHz, which is approximately the highest frequency that can be detected by the human ear. However, the acoustic microscopes emit ultrasound ranging from 5 MHz to beyond 400 MHz so that micrometre
60-meter band bandplan strongly recommends that the WRC-15 frequencies should only be used if other 5 MHz frequencies, allocated under Article 4.4, are not available. It does not require stations to adopt the USB dial frequencies of 5354, 5357, 5360 and 5363 kHz but these frequencies provide a good fit with the American channel on 5357 kHz, and UK stations which can use 5354 and 5363 kHz (but not the middle two). Also, it is only by using these exact frequencies that there will be enough room for four simultaneous SSB conversations without mutual interference, assuming the 2.8 kHz "de facto" standard