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. <EOS>