A method comprising: providing a first communication system comprising at least one microphone and at least one loudspeaker, wherein the microphone is positioned at the front of an enclosed environment, and the loudspeaker is positioned at the rear of the enclosed environment; providing a second communication system comprising at least one microphone and at least one loudspeaker, wherein the microphone is positioned at the rear of the enclosed environment, and the loudspeaker is positioned at the front of the enclosed environment; for each communication system, transforming a signal received by a first one of the microphones at a given position of the other communication system, to the frequency domain; determining a noise level estimate for the transformed signal; determining a speech level estimate for the transformed signal; determining a SNR at the given position from the noise and speech level estimates; and determining a gain for the transformed signal to achieve a selected SNR range at the given position, wherein determining the gain comprises: adapting an actual gain to follow a target gain, wherein the target gain is adjusted to achieve the selected SNR range; comparing the target gain and the actual gain to determine a gain change increment; increasing the actual gain by the gain change increment if the SNR at the given position is lower than a minimum SNR in the SNR range; and decreasing the actual gain by the gain change increment if the SNR at the given position is higher than a maximum SNR in the SNR range. providing a first communication system comprising at least one microphone and at least one loudspeaker, wherein the microphone is positioned at the front of an enclosed environment, and the loudspeaker is positioned at the rear of the enclosed environment; providing a second communication system comprising at least one microphone and at least one loudspeaker, wherein the microphone is positioned at the rear of the enclosed environment, and the loudspeaker is positioned at the front of the enclosed environment; for each communication system, transforming a signal received by a first one of the microphones at a given position of the other communication system, to the frequency domain; determining a noise level estimate for the transformed signal; determining a speech level estimate for the transformed signal; determining a SNR at the given position from the noise and speech level estimates; and determining a gain for the transformed signal to achieve a selected SNR range at the given position, wherein determining the gain comprises: adapting an actual gain to follow a target gain, wherein the target gain is adjusted to achieve the selected SNR range; comparing the target gain and the actual gain to determine a gain change increment; increasing the actual gain by the gain change increment if the SNR at the given position is lower than a minimum SNR in the SNR range; and decreasing the actual gain by the gain change increment if the SNR at the given position is higher than a maximum SNR in the SNR range. adapting an actual gain to follow a target gain, wherein the target gain is adjusted to achieve the selected SNR range; comparing the target gain and the actual gain to determine a gain change increment; increasing the actual gain by the gain change increment if the SNR at the given position is lower than a minimum SNR in the SNR range; and decreasing the actual gain by the gain change increment if the SNR at the given position is higher than a maximum SNR in the SNR range.