Techniques have been developed for transmitting and receiving information conveyed through the air from one portable device to another as a generally unperceivable coding within an otherwise recognizable acoustic signal. For example, in some embodiments in accordance with the present invention(s), information is acoustically communicated from a first handheld device toward a second by encoding the information in a signal that, when converted into acoustic energy at an acoustic transducer of the first handheld device, is characterized in that the acoustic energy is discernable to a human ear yet the encoding of the information therein is generally not perceivable by the human. The acoustic energy is transmitted from the acoustic transducer of the first handheld device toward the second handheld device across an air gap that constitutes a substantially entirety of the distance between the devices. Acoustic energy received at the second handheld device may then be processed using signal processing techniques tailored to detection of the particular information encodings employed.