Controlling loudness of speech in signals that contain speech and other types of audio material

#The present invention is related to audio systems and methods that are concerned with the measuring and controlling of the loudness of speech in audio signals that contain speech and other types of audio material.

#While listening to radio or television broadcasts, listeners frequently choose a volume control setting to obtain a satisfactory loudness of speech. The desired volume control setting is influenced by a number of factors such as ambient noise in the listening environment, frequency response of the reproducing system, and personal preference. After choosing the volume control setting, the listener generally desires the loudness of speech to remain relatively constant despite the presence or absence of other program materials such as music or sound effects.

#When the program changes or a different channel is selected, the loudness of speech in the new program is often different, which requires changing the volume control setting to restore the desired loudness. Usually only a modest change in the setting, if any, is needed to adjust the loudness of speech in programs delivered by analog broadcasting techniques because most analog broadcasters deliver programs with speech near the maximum allowed level that may be conveyed by the analog broadcasting system. This is generally done by compressing the dynamic range of the audio program material to raise the speech signal level relative to the noise introduced by various components in the broadcast system. Nevertheless, there still are undesirable differences in the loudness of speech for programs received on different channels and for different types of programs received on the same channel such as commercial announcements or “commercials” and the programs they interrupt.

#FIG. 1 is a schematic block diagram of an audio system that may incorporate various aspects of the present invention.

#FIG. 2 is a schematic block diagram of an apparatus that may be used to control loudness of an audio signal containing speech and other types of audio material.

#FIG. 3 is a schematic block diagram of an apparatus that may be used to generate and transmit audio information representing an audio signal and control information representing loudness of speech.

#FIG. 1 is a schematic block diagram of an audio system in which the transmitter 2 receives an audio signal from the path 1, processes the audio signal to generate audio information representing the audio signal, and transmits the audio information along the path 3. The path 3 may represent a communication path that conveys the audio information for immediate use, or it may represent a signal path coupled to a storage medium that stores the audio information for subsequent retrieval and use. The receiver 4 receives the audio information from the path 3, processes the audio information to generate an audio signal, and transmits the audio signal along the path 5 for presentation to a listener.

#The system shown in FIG. 1 includes a single transmitter and receiver; however, the present invention may be used in systems that include multiple transmitters and/or multiple receivers. Various aspects of the present invention may be implemented in only the transmitter 2, in only the receiver 4, or in both the transmitter 2 and the receiver 4.

#In one implementation, the transmitter 2 performs processing that encodes the audio signal into encoded audio information that has lower information capacity requirements than the audio signal so that the audio information can be transmitted over channels having a lower bandwidth or stored by media having less space. The decoder 4 performs processing that decodes the encoded audio information into a form that can be used to generate an audio signal that preferably is perceptually similar or identical to the input audio signal. For example, the transmitter 2 and the receiver 4 may encode and decode digital bit streams compliant with the AC-3 coding standard or any of several standards published by the Motion Picture Experts Group (MPEG). The present invention may be applied advantageously in systems that apply encoding and decoding processes; however, these processes are not required to practice the present invention.