A pump, comprising: a reservoir configured to deliver a liquid; a port coupled to the reservoir and configured to discharge the liquid; a reference-volume assembly, wherein the reference-volume assembly comprises: a reference-volume chamber; a speaker disposed within the reference-volume chamber; and a reference microphone disposed within the reference-volume chamber, characterized in that the pump further comprises: a plunger having a piston coupled to a shaft, wherein the piston is disposed within the reservoir in sliding engagement with an inner surface of the reservoir, wherein the piston defines a liquid side of the reservoir and a non-liquid side of the reservoir whereby movement of the plunger towards the liquid side of the reservoir discharges liquid through the port; an additional reservoir configured to deliver an additional liquid; an additional port coupled to the additional reservoir and configured to discharge the additional liquid; and an additional plunger having an additional piston coupled to an additional shaft, wherein the additional piston is disposed within the additional reservoir in sliding engagement with an inner surface of the additional reservoir, wherein the additional piston defines a liquid side of the additional reservoir and a non-liquid side of the additional reservoir whereby movement of the additional plunger towards the liquid side of the additional reservoir discharges liquid through the additional port, wherein the reference-volume assembly is coupled to the reservoir at an opposite end of the reservoir relative to the port, wherein the reference-volume assembly is further coupled to the additional reservoir at an opposite end of the additional reservoir relative to the additional port, and wherein the reference-volume chamber is in acoustic communication with the non-liquid side of the reservoir, wherein the reference-volume chamber is further in acoustic communication with the non-liquid side of the additional reservoir. a reservoir configured to deliver a liquid; a port coupled to the reservoir and configured to discharge the liquid; a reference-volume assembly, wherein the reference-volume assembly comprises: a reference-volume chamber; a speaker disposed within the reference-volume chamber; and a reference microphone disposed within the reference-volume chamber, a reference-volume chamber; a speaker disposed within the reference-volume chamber; and a reference microphone disposed within the reference-volume chamber, characterized in that the pump further comprises: a plunger having a piston coupled to a shaft, wherein the piston is disposed within the reservoir in sliding engagement with an inner surface of the reservoir, wherein the piston defines a liquid side of the reservoir and a non-liquid side of the reservoir whereby movement of the plunger towards the liquid side of the reservoir discharges liquid through the port; an additional reservoir configured to deliver an additional liquid; an additional port coupled to the additional reservoir and configured to discharge the additional liquid; and an additional plunger having an additional piston coupled to an additional shaft, wherein the additional piston is disposed within the additional reservoir in sliding engagement with an inner surface of the additional reservoir, wherein the additional piston defines a liquid side of the additional reservoir and a non-liquid side of the additional reservoir whereby movement of the additional plunger towards the liquid side of the additional reservoir discharges liquid through the additional port, a plunger having a piston coupled to a shaft, wherein the piston is disposed within the reservoir in sliding engagement with an inner surface of the reservoir, wherein the piston defines a liquid side of the reservoir and a non-liquid side of the reservoir whereby movement of the plunger towards the liquid side of the reservoir discharges liquid through the port; an additional reservoir configured to deliver an additional liquid; an additional port coupled to the additional reservoir and configured to discharge the additional liquid; and an additional plunger having an additional piston coupled to an additional shaft, wherein the additional piston is disposed within the additional reservoir in sliding engagement with an inner surface of the additional reservoir, wherein the additional piston defines a liquid side of the additional reservoir and a non-liquid side of the additional reservoir whereby movement of the additional plunger towards the liquid side of the additional reservoir discharges liquid through the additional port, wherein the reference-volume assembly is coupled to the reservoir at an opposite end of the reservoir relative to the port, wherein the reference-volume assembly is further coupled to the additional reservoir at an opposite end of the additional reservoir relative to the additional port, and wherein the reference-volume chamber is in acoustic communication with the non-liquid side of the reservoir, wherein the reference-volume chamber is further in acoustic communication with the non-liquid side of the additional reservoir.