Bluetooth Speaker Audio Processing

ECE438 Fall 2014
Prof. Mireille Boutin

Chloe Kauffman

Motivation for this page is accredited to noticeably poor sound quality from my Bluetooth headphones while connected to my laptop. This page will explore audio codecs used in Bluetooth devices, specifically audio compression formats and how transmitting device compatibility can result in an altered audio signal and therefore sound quality.

Bluetooth operates in the Industrial, Scientific, Medical (ISM) frequency band at 2.4 GHz to 2.4835 GHz. It uses frequency division spread spectrum communications, also known as frequency hopping spread spectrum (FHSS). [1]
The spectrum is divided into 79 channels. Bandwidth is limited to 1 MHz per channel. Each channel is divided in time into slots which each correspond to an RF hop frequency. [1] The data can use asynchronous connection-less mode (ACL) which requires the headers to contain the address destination and packet-switching, and synchronous connection-oriented (SCO) mode operating at up to 64 kbps per link with a max of three links per two devices. Both these audio channels can operate simultaneously. [1]

[1] Pohlmann, K. C. (2011). Digital Audio (6th ed.). New York, NY: McGraw Hill.

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