A system for acoustic sensing and communication, the system comprising: a distributed acoustic sensing optical fiber disposed in a downhole environment with a downhole component; an optical interrogation device including an optical signal source configured to inject an optical signal into the DAS optical fiber and a receiver configured to detect return signals reflected from sensing locations in the DAS optical fiber; an acoustic telemetry unit connected to the downhole component, wherein the acoustic telemetry unit is disposed in the downhole environment, the acoustic telemetry unit configured to receive a communication from the downhole component and generate an acoustic signal having a frequency within a selected frequency range and encoded to carry the communication, wherein the acoustic telemetry unit includes a plurality of acoustic telemetry units arrayed along the DAS optical fiber, characterised by: at least one of the plurality of acoustic telemetry units configured to generate an acoustic signal having a frequency that is different than at least another of the plurality of acoustic telemetry units, each acoustic signal applied to a respective first section of the DAS optical fiber; wireless sensors that are pumped downhole with fluid through the borehole and/or into a formation, wherein each wireless sensor is equipped with an acoustic transmitter that can be used to track the position of the wireless sensor and/or receive data from the wireless sensor via the DAS optical fiber; and a processor (42, 56) configured to associate a first portion of the return signals with the respective first section of the DAS optical fiber to which the acoustic signal is applied and reproduce the communication based on the first portion of the return signals associated with the respective first section of the DAS optical fiber, and associate a second portion of the return signals with a second section of the DAS optical fiber to detect one or more acoustic events generated by the downhole environment, wherein the system is configured to detect acoustic signals emitted from the wireless sensors. a distributed acoustic sensing optical fiber disposed in a downhole environment with a downhole component; an optical interrogation device including an optical signal source configured to inject an optical signal into the DAS optical fiber and a receiver configured to detect return signals reflected from sensing locations in the DAS optical fiber; an acoustic telemetry unit connected to the downhole component, wherein the acoustic telemetry unit is disposed in the downhole environment, the acoustic telemetry unit configured to receive a communication from the downhole component and generate an acoustic signal having a frequency within a selected frequency range and encoded to carry the communication, wherein the acoustic telemetry unit includes a plurality of acoustic telemetry units arrayed along the DAS optical fiber, characterised by: at least one of the plurality of acoustic telemetry units configured to generate an acoustic signal having a frequency that is different than at least another of the plurality of acoustic telemetry units, each acoustic signal applied to a respective first section of the DAS optical fiber; wireless sensors that are pumped downhole with fluid through the borehole and/or into a formation, wherein each wireless sensor is equipped with an acoustic transmitter that can be used to track the position of the wireless sensor and/or receive data from the wireless sensor via the DAS optical fiber; and a processor (42, 56) configured to associate a first portion of the return signals with the respective first section of the DAS optical fiber to which the acoustic signal is applied and reproduce the communication based on the first portion of the return signals associated with the respective first section of the DAS optical fiber, and associate a second portion of the return signals with a second section of the DAS optical fiber to detect one or more acoustic events generated by the downhole environment, wherein the system is configured to detect acoustic signals emitted from the wireless sensors. at least one of the plurality of acoustic telemetry units configured to generate an acoustic signal having a frequency that is different than at least another of the plurality of acoustic telemetry units, each acoustic signal applied to a respective first section of the DAS optical fiber; wireless sensors that are pumped downhole with fluid through the borehole and/or into a formation, wherein each wireless sensor is equipped with an acoustic transmitter that can be used to track the position of the wireless sensor and/or receive data from the wireless sensor via the DAS optical fiber; and a processor (42, 56) configured to associate a first portion of the return signals with the respective first section of the DAS optical fiber to which the acoustic signal is applied and reproduce the communication based on the first portion of the return signals associated with the respective first section of the DAS optical fiber, and associate a second portion of the return signals with a second section of the DAS optical fiber to detect one or more acoustic events generated by the downhole environment, wherein the system is configured to detect acoustic signals emitted from the wireless sensors.