For those still using analogue or digital phone systems, voice on ISDN circuits has a bandwidth of around 4000Hz. The audio from an analogue phone is sampled at 8000Hz, and because of the nyquist theorem, must be low-pass filtered to 4000Hz. So any frequencies in the audio beyond 4000Hz are lost. Interestingly, the human ear and mind are good at recognising human speech, so this is considered "toll-quality" voice, i.e. good enough to pay for. This is the reason why certain vocalised letters are difficult or impossible to tell apart on the phone. For example, the differences between B, P, T, C, etc. are almost entirely above 4000Hz.
Did you know that at Parabolic you get individualized, one-on-one Physical Therapy sessions, and that we spend more direct, hands-on time with you than you’ll get at other Physical Therapy facilities? Well, it’s true-we purposefully limit the number of clients we take on so we can devote more time to improving each client’s health and performance. You can see for yourself how we set the standard in rehab and sports performance – just schedule your consultation today.

Need on hold music for your business phone line? On hold music is a necessity for any client facing business phone system. Use on hold music as an opportunity not only to help your client pass time while waiting but to affirm your brand identify as well.
Curation by context is the game of late. We choose music by our mood, by our activity, and by our audience. Spotify lets you browse by mood and events, showcasing playlists that cross multiple genres because music can’t be sorted into individual boxes.