SUMMARYWe propose "Ubiquitous Acoustic Spaces," in which each sound source can emit some address information with audio signals and allow automatic access to its related cyber space, using handheld devices such as cell phones. In order to realize this concept, we have considered three types of extraction methods: acoustic modulation, audio fingerprints, and audio watermarking. We have proposed a novel audio watermarking technique, which allows contactless asynchronous detection of embedded audio watermarks through speaker and microphone devices. However, its embedding data rate was around 10 bps, which was not sufficient for embedding generally used URL address texts.Therefore, we have extended the embedding frequency range and proposed a duplicated embedding algorithm, which uses both the previously proposed frequency division method and the temporal division method together. By these improvements, the possible embedding data rate could be extended to 61.5 bps, and we could extract watermarks through public telephone networks, even from a cell phone sound source.In this paper, we describe our improved watermark embedding and extracting algorithms, and present experimental results on watermark extraction precision under several audio signal capturing conditions.