SIGNAL PROCESSING APPARATUS AND SIGNAL PROCESSING METHOD, ENCODER AND ENCODING METHOD, DECODER AND DECODING METHOD, AND PROGRAM TECHNICAL FIELD [0001] The present invention relates to a signal processing apparatus and a signal processing method, an encoder and an 10 encoding method, a decoder and a decoding method, and a program, and more particularly to a signal processing apparatus and a signal processing method, an encoder and an encoding method, a decoder and a decoding method, and a program for reproducing a music signal with improved sound quality by expansion of 15 a frequency band. BACKGROUND ART [0002] Recently, music distribution services for distributing 20 music data via the internet have been increased. The music distributionser_vice distributes; as music data, encod(d data obtained by encoding a music signal. As an encoding method of the music signal, an encoding method has been commonly used in which the encoded data file size is suppressed to decrease 25 a bit rate so as to save time during download. [0003] Such an encoding method of the music signal is broadly divided into an encoding method such as MP3 (MPEG (Moving Picture Experts Group) Audio Layers 3) (International Standard 30 ISO/IEC 11172-3) and an encoding method such as HE-AAC (High Efficiency MPEG4 AAC) (International Standard ISO/IEC I SP2484'7'7WO03 14496-3). [0004] The encoding method represented by MP3 cancels a signal component of a high frequency band (hereinafter, referred to as a high band) having about 15 kHz or more in music signal that is almost imperceptible to humans, and encodes the low frequency band (hereinafter, referred to as a low band) of the signal component of the remainder. Therefore, the encoding method is referred to as a high band cancelation 10 encoding method. This kind of high band cancelation encoding method can suppress the file size of encoded data. However, since sound in a high band can be perceived slightly by human, if sound is produced and output from the decoded music signal obtained by decoding the encoded data, suffers a loss of sound 15 quality whereby a sense of realism of an original sound is lost and a sound quality deterioration such a blur of sound occurs. [0005] Unlike this, the encoding method represented by HE-AAC 20 extracts specific information from a signal component of the high band and encodes the information in conjunction with a signal component of the low band. The encoding method is referred to below as a high band characteristic encoding method. Since the high band characteristic encoding method encodes 25 only characteristic information of the signal component of the high band as information on the signal component of the high band, deterioration of sound quality is suppressed and encoding efficiency can be improved. [0006] 30 In decoding data encoded by the high band characteristic encoding method, the signal component of the low band and SP248477WO03 characteristic information are decoded and the signal component of the high band is produced from a signal component of the low band and characteristic information after being decoded. Accordingly, a technology that expands a frequency band of the signal component of the high band by producing a signal component of the high band from signal component of the low band is referred to as a band expansion technology. [0007] - As an application example of a band expansion method, 10 after decoding of data encoded by a high band cancelation encoding method, a post process is performed. In the post process, the high band signal component lost in the encoding is generated from the decoded low band signal component, thereby expanding the frequency band of the signal component 15 of the low band (see Patent Document 1). The method of frequency band expansion of the related art is referred below to as a band expansion method of Patent Document 1. [0008] In a band expansion method of the Patent Document 1, 20 the apparatus estimates a power spectrum (hereinafter, suitably referred to as a frequency envelope of the high band) of the high band from the power spectrum of an input signal by setting the signal component of the low band after decoding as the input signal and produces the signal component of the 25 high band having the frequency envelope of the high band from the signal component of the low band. [0009] Fig. 1 illustrates an example of a power spectrum of the lowband after the decoding as an input signal and a frequency 30 envelope of an estimated high band. [0010] SP248477WO03 In Fig. 1, the vertical axis illustrates a power as a logarithm and a horizontal axis illustrates a frequency. [0011] The apparatus determines the band in the low band of the signal component of the high band (hereinafter, referred to as an expansion start band) from a kind of an encoding system on the input signal and information such as a sampling rate, a bit rate and the like (hereinafter, referred to as side information)- Next, the apparatus divides the input signal 10 as signal component of the low band into a plurality of sub--band signals. The apparatus obtains a plurality of sub-band signals after division, that is, an average of respective groups (hereinafter, referred to as a group power) in a time direction of each power of a plurality of sub-band signals 15 of alowbandside lower than the expansion start band is obtained (hereinafter, simply referred to as a low band side). As illustrated in Fig. 1, according to the apparatus, it is assumed that the average of respective group powers of the signals of a plurality of sub-bands of the low band side is a power 20 and a point making a frequency of a lower end of the expansion sLart band be as frequency is a starting point. The apparatus estimates a primary straight line of a predetermined slope passing through the starting point as the frequency envelope of the high band higher than the expansion start band 25 (hereinafter, simply referred to as a high band side). In addition, a position in a power direction of the starting point may be adjusted by a user. The apparatus produces each of a plurality of signals of a sub-band of the high band side from a plurality of signals of a sub-band of the low band side 30 to be an estimated frequency envelope of the high band side The apparatus adds a plurality of the produced signals of the 4 SP243477WO03 sub-band of the high band side to each other into the signal components of the high band and adds the signal components of the low band to each other to output the added signal components. Therefore, the music signal after expansion of 5 the frequency band is close to the original music signal. However, it is possible to produce the music signal of a better quality. [0012] The band expansion method disclosed in the Patent 10 Document 1 has an advantage that the frequency band can be expanded for the music signal after decoding of the encoded data with respect to various high band cancelation encoding methods and encoded data of various bit rates. 15 CITATION LIST PATENT DOCUMENT [0013] Patent Document 1a Japanese Patent Application Laid-Open No. 2008-139844 20 SUMMARY OF TEE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION [OOI-4] Accordingly, the band expansion method disclosed in 25 Patent Document 1 may be improved in that the estimated frequency envelope of a high band side is a primary straight line of a predetermined slope, that is, a shape of the frequency envelope is fixed. [0015] 30 In other words, the power spectrum of the music signal has various shapes and the music signal has a lot of cases SP248477WO03 where the frequency envelope of the high band side, estimated by the band expansion method disclosed in Patent Document 1 deviates considerably. [0016] Fig. 2 illustrates an example of an original power spectrumof anattackmusic signal (attackmusic signal) having a rapid change in time as a drum is strongly hit once. [0017] In addition,, Fig. 2 also illustrates the frequency 10 envelope of the high band side estimated from the input signal by setting the signal component of the low band side of the attack relative music signal as an input signal by the band expansion method disclosed in the Patent Document 1. [0018] 15 As illustrated in Fig. 2, the power spectrum of the original high band side of the attack music signal has a substantially flat shape. [0019] Unlike this, the estimated frequency envelope of the 20 high band side has a predetermined negative slope and even if the frequency is adjusted to have the power closes t:o the original power spectrum , difference between the power and the original power spectrum becomes large as the frequency becomes high. 25 [0020] Accordingly, in the band expansion method disclosed in Patent Document 1, the estimated frequency envelope of the high band side cannot reproduce the frequency envelope of the original high band side with high accuracy. Therefore, if 30 sound fromthemusic signal after the expansion of the frequency band is produced and output, clarity of the sound in auditory SP248477WO03 is lower than the original sound. [0021] In addition, in.the high band characteristic encoding method such as HE-AAC and the like described above, the 5 frequency envelope of the high band side is used as characteristic information of the encoded high band signal components. However, it needs to reproduce the frequency envelope of the original high band side with high accuracy in a decoding side. 10 [0022] The present invention has been made in a consideration of such a circumstance and provides a music signal having a better sound quality by expanding a frequency band. 15 SOLUTIONS TO PROBLEMS [0023] As ignalprocessing apparatus according to a first aspect of the present invention includes: a demultiplexing unit that demultiplexes input encoded data to at least low band encoded 20 data and coefficient information; a low band decoding unit that decodes the low band encoded data to produce low band signals; a selection unit that selects a coefficient table which is obtained based on the coefficient information among a plurality of coefficient tables used for the production of 25 high band signals and having coefficients for the respective sub-bands on a high band side; an extension and reduction unit that deletes the coefficients of some sub-bands to reduce the coefficientt table or produces the coefficients of predetermined sub-bands based on the coefficients of some 30 sub-bands to extend the coefficient table; a high band sub-band power calculation unit that calculates high band sub-band SP248477W003 powers of high band sub-band signals of the respective sub-bands constituting the high band signals based on low band sub-band signals of the respective sub-bands constituting the low band signals and the extended or reduced coefficient table; and a high band signal production unit that produces the high band signals based on the high band sub-band powers and the low band sub-band signals. [0024] The extension and reduction unit may duplicate the 10 coefficients of a sub-band having a highest frequency which is included in the coefficient table and set the duplicated coefficients to coefficients of a sub-band having a higher frequency than the highest frequency to extend the coefficient tables 15 [0025] The extension and reduction unit may delete the coefficients of a sub-band, which has a higher frequency than that of a sub-band having a highest frequency among sub-bands of the high band sub-band signals, from the coefficient table 20 to reduce the coefficient table. [0026] A signal processing method or a program according to the first aspect of the invention includes the steps of demultiplexing input encoded data to at least low band encoded 25 data and coef f icient inf ormation; decoding the lowband encoded data to produce lowband signals; selecting a coefficient table which is obtained based on the coefficient information among a plurality of coefficient tables used for the production of high band signals and having coefficients for the respective 30 sub-bands on a high band side; deleting the coefficients of some sub-bands to reduce the coefficient table or generating S2248477WO03 the coefficients of predetermined sub-bands based on the coefficients of some sub-bands to extend the coefficient table; calculating high band sub-band powers of high band sub-band signals of the respective sub-bands constituting the high band 5 signals based on low band sub-band signals of the respective sub-bands constituting the low band signals and the extended or reduced coefficient table; and generating the high band signals based on the high band sub-band powers and the low band sub-band signals. 10 [0027] According to the first aspect of the invention, input encoded data is demultiplexed to at least low band encoded data and coefficient information; the low band encoded data is decoded to produce low band signals ; a coefficient table 15 which is obtained based on the coefficient information is selected among a plurality of coefficient tables used for the production of high band signals and having coefficients for the respective sub-bands on a high band side; the coefficients of some sub -bands are deleted to reduce the coefficient table 20 or the coefficients of predetermined sub-bands are produced based on the coefficients of some sub-bands to extend the coefficient table ; high band sub-band powers of high band subrband signals of the respective sub-bands constituting the high band signals are calculated based on low band sub-band 25 signals of the respective sub-bands constituting the low band signals and the extended or reduced coefficient table; and the high band signals are produced based on the high band sub-band powers and the low band sub-band signals. [0028] 30 A signal processing apparatus according to a second aspect of the present invention includes : a sub-band division SP248477WO03 unit that produces low band sub-band signals of a plurality of sub-bands on a low band side of an input signal and high band sub-band signals.of a plurality of sub-bands on a high band side of the input signal; an extension and reduction unit 5 that deletes the coefficients of some sub-bands to reduce a coefficient table or produces coefficients of predetermined sub-bands based on coefficients of some sub-bands to extend a coefficient table, the coefficient table having the coefficients for the respective sub-bands on the high band 10 side, a pseudo high band sub-band power calculation uni L that calculates pseudo high band sub-band powers, which are estimated values of powers of the high band sub-band signals, for the respective sub-bands on the high band side based on the extended or reduced coefficient table and the low band 15 sub-band signals; a selection unit that compares high band sub-band powers of the high band sub-band signals and the pseudo high band sub-band powers to each other and selects one of a plurality of the coefficient tables; and a production unit that produces data containing coefficient information for 20 obtaining the selected coefficient table. [00291 The extension and reduction unit may duplicate the coefficients of a sub-band having a highest frequency which is included in the coefficient table and set the duplicated 25 coefficients to coefficients of a sub-band having a higher frequency than the highest frequency to extend the coefficient table. [0030] The extension and reduction unit may delete the 30 coefficients of a sub-band, which has a higher frequency than that of a sub-band having a highest frequency among sub-bands 10 SP248477WO03 of the high band sub-band signals, from the coefficient table to reduce the coefficient table. [0031] A signal processing method or a program according to 5 the second aspect of the invention includes the steps of generating low band sub-band signals of a plurality of sub-bands on a low band side of an input signal and high band sub-band signals of a plurality of sub-bands on a high band side of the input signal; deleting the coefficients of some 10 sub-bands to reduce a coefficient table or generating coefficients of predetermined sub-bands based on coefficients of some sub-bands to extend a coefficient table, the coefficient table having the coefficients for the respective sub-bands on the high band side; calculating pseudo high band 15 sub-band powers, which are estimated values of powers of the high band sub-band signals, for the respective sub-bands on the high band side based on the extended or reduced coefficient table and the low band sub--band signals; comparing high band sub-band powers of the high band sub-band signals and the pseudo 20 high band sub-band powers to each other and selecting one of a plurality of the coefficient tables; and generating data containing coefficient information for obtaining the selected coefficient table. [00321 25 According to the second aspect of the invention, low band sub--band signals of a plurality of sub-bands on a low band side of an input signal and high band sub--band signals of a plurality of sub-bands on a high band side of the input signal are produced; the coefficients of some sub-bands are 30 deleted to reduce a coefficient table or coefficients of predetermined sub-bands are produced based on coefficients 11 SP248477WO03 of some sub-bands to extend a coefficient table, the coefficient table having the coefficients for the respective sub-bands on the high.band side; pseudo high hand sub-band powers, which are estimated values of powers of the high band 5 sub-band signals, are calculated for the respective sub-bands on the high band side based on the extended or reduced coefficient table and the low band sub-band signals; high band sub-band powers of the high band sub-band signals and the pseudo high band sub-band powers are compared to each other and one 10 of a plurality of the coefficient tables is selected; and data containing coefficient information for obtaining the selected coefficient table is produced. [0033] A decoder according to a third aspect of the present 15 invention includes: a demultiplexing unit that demultiplexes input encoded data to at least low band encoded data and coefficient information; a low band decoding unit that decodes the low band encoded data to produce,low band signals; a selection unit that selects a coefficient table which is 20 obtained based on the coefficient information among a plurality of coefficient tables used for the production of high band signals and having coefficients for the respective sub-bands on a _high band side; an extension and reduction unit that deletes the coefficients of some sub-bands to reduce the coefficient 25 table or produces the coefficients of predetermined sub-bands based on the coefficients of some sub-bands to extend the coefficient table; a high band sub-band power calculation unit that calculates high band sub-band powers of high band sub-band signals of the respective sub-bands constituting the high band 30 signals based on low band sub-band signals of the respective sub-bands constituting the low band signals and the extended SP248477WO03 or reduced coefficient table; a high band signal production unit that produces the high band signals based on the high band sub-band powers and the low band sub-band'signals; and a synthesis unit that synthesizes the low band signal and the high band signal with each other to produce an output signal . [0034] A decoding method according to the third aspect. of the invention includes the steps of demultiplexing input encoded data to at least low band encoded data and coefficient 10 information; decoding the low band encoded data to produce low band signals; selecting a coefficient table which is obtained based on the coefficient information among aplurality of coefficient tables used for the production of high band signals and having coefficients for the respective sub-bands 15 on a highband side; deleting the coefficients of some sub-bands to reduce the coefficient table or generating the coefficients of predetermined sub-bands based on the coefficients of some sub-bands to extend the coefficient table; calculating high band sub-band powers of high band sub-band signals of the 20 respective sub-bands constituting the high band signals based on 1ow band sub-band signals of the respective sub-bands constituting the low band signals and the extended or reduced coefficient table; generating the high band signals based on the highband sub-bandpowers and the lowband sub-band signals; 25 and synthesizing the low band signal and the high band signal with each other to produce an output signal, [0035] According to the third aspect of the invention, input encoded data is demultiplexed to at least low band encoded 30 data and coefficient information; the low band encoded data is decoded to produce low band signals; a coefficient table 13 SP248477WO03 which is obtained based on the coefficient information is selected among a plurality of coefficient, tables used for the production of high band signals and having coefficients for the respective sub-bands on a high band side; the coefficients 5 of some sub-bands are deleted to reduce the coefficient table or the coefficients of predetermined sub-bands are produced based on the coefficients of some sub-bands to extend the coefficient table; high band sub-band powers of high band sub-band signals of the respective sub-bands constituting the 10 high band signals are calculated based on low band sub-band signals of the respective sub-bands constituting the low band signals and the extended or reduced coefficient table; the high band signals ate produced based on the high band sub-band powers and the low band sub-band signals; and the low band 15 signal and the high band signal are synthesized with each other to produce an output signal. [0036] An encoder according to a fourth aspect of the present invention includes: a sub-band division unit that produces 20 low band sub-band signals of a plurality of sub-bands on a low band side of an input signal and high band sub-band signals of a plurality of sub-bands on a high band side of the input signal; an extension and reduction unit that deletes the coefficients of some sub-bands to reduce a coefficient table 25 or produces coefficients of predetermined sub-bands based on coefficients of some sub-bands to extend a coefficient table, the coefficient table having coefficients for the respective sub-bands on the high band side; a pseudo high band sub-band power calculation unit that calculates pseudo high band 30 sub-band powers, which are estimated values of powers of the high band sub-band signals, for the respective sub-bands on 14 SP248477WO03 the high band side based on the extended or reduced coefficient table and the low band sub-band signals; a,selection unit that compares high band sub-band powers of the high band sub-band signals and the pseudo high band sub-band powers to each other and selects one of a plurality of the coefficient tables; a high band encoding unit that encodes coefficient information for obtaining the selected coefficient table to produce high band encoded data; a low band encoding unit that encodes low band signals of the input signal to produce low band encoded 10 data; and a multiplexing unit that multiplexes the low band encoded data and the high band encoded data to produce an output code string. [0037] An encoding method according the fourth aspect of the 15 invention includes the steps of generating low band sub-band. signals of a plurality of sub-bands on a low band side of an input signal and high band sub-band signals of a plurality of sub-bands on a high band side of the input signal; deleting the coefficients of some sub-bands to reduce a coefficient 20 table or generating coefficients of predetermined sub-bands based on coefficients of some sub-bands to extend a coot LLcient table, the coefficient table having coefficients for the respective sub-bands on the high band side; calculating pseudo high band sub-bandpowers, which are estimated values of powers 25 of the high band sub-band signals, for the respective sub-bands on the high band side based on the extended or reduced coefficient table and the low band sub-bandsignals;comparing - high band sub-band powers of the high band sub-band signals and the pseudo high band sub-band powers to each other and 30 selecting one of a plurality of the coefficient tables; encoding coefficient information for obtaining the selected 15 SP248477WO03 coefficient table to produce high band encoded data; encoding low bands ignals of the input signal to produce low band encoded data; and multiplexing the low band encoded data and the high band encoded data to produce an output code string. [0038] According to the fourth aspect of the invention, low band sub-band signals of a plurality of sub-bands on_a low band side of an input signal and high band sub-band signals of a plurality of sub-bands on a high band side of the input 10 signal are produced; the coefficients of some sub-bands are deleted to reduce a coefficient table or coefficients of predetermined sub-bands are produced based on coefficients of some sub-bands to extend a coefficient table, the coefficient table having coefficients for the respective 15 sub-bands on the high band side; pseudo high band sub-band powers, which are estimated values of powers of the high band sub-band signals, are calculated for the respective sub-bands on the high band side based on the extended or reduced coefficient table and the low band sub-band signals; high band 20 sub-bandpowers of the high band sub-band signals and the pseudo high band sub -band powers are compared to each other anci one of a plurality of the coefficient tables is selected; coefficient information for obtaining the selected coefficient table is encoded to produce high band encoded data; 25 low band signals of the input signal are encoded to produce low band encoded data; and the low band encoded data. and the high band encoded data are multiplexed to produce an output code string. 30 EFFECTS OF THE INVENTION [0039] 16 SP2484'77WO03 According to the first embodiment to the fourth embodiment, it is possible to reproduce music signal with high sound quality by expansion of a frequency band. 5 BRIEF DESCRIPTION OF DRAWINGS [0040] Fig. 1 is a view an example of illustrating in an example of a power spectrum of a low band after decoding an input signal and a frequency envelope of a high band estimated. 10 Fig. 2 is a view illustrating an example of an original power spectrum of music signal of an attack according to rapid change in time. Fig. 3 is a block diagram illustrating a functional configuration example of a frequency band expansion apparatus 15 in a first embodiment of the present invention. Fig. 4 is a flowchart illustrating an example of a frequency band expansion process by a frequency band expansion apparatus in Fig. 3. Fig. 5 is a view illustrating arrangement of a power 20 spectrum of signal input to a frequency band expansion apparatus in Fig.. 3 and arrangement on a frequency axis of a band pass filter. Fig. 6 is a view illustrating an example illustrating frequency characteristics of a vocal region and a power 25 spectrum of a high band estimated. Fig. 7 is a view illustrating an example of a power spectrum of signal input to a frequency band expansion apparatus in Fig. 3. Fig. 8 is a. view illustrating an example of a power vector 30 after liftering of an input signal in Fig. 7. Fig. 9 is a block diagram illustrating a functional 17 S2248477WO03 configuration example of a coefficient learning apparatus for performing learning of a coefficient used in a high band signal production circuit of a frequency band expansion apparatus in Fig. 3. 5 Fig. 10 is a flowchart describing an example of a coefficient learning process by a coefficient learning apparatus in Fig. 9. Fig. 11 is a block diagram illustrating a functional configuration example of an encoder in a second embodiment 10 of the present invention. Fig. 12 is a flowchart describing an example of an encoding process by an encoder in Fig. 11. Fig. 13 is a block diagram illustrating a functional configuration example of a decoder in a second embodiment of 15 the present invention. Fig. 7.4 is a flowchart describing an example of a decoding processing by a decoder in Fig. 13. Fig. 15 is a block diagram illustrating a functional configuration example of a coefficientlearning apparatus for 20 performing learning of a representative vector used in a. high band encoding circuit of an encoder in Fiq. 11 and (! ,, coded high band sub-band power estimation coefficient used in a high band decoding circuit of decoder in Fig. 13. Fig. 16 is a flowchart describing an example of a 25 coefficient learning process by a coefficient learning apparatus in Fig. 15. Fig. 17 is a view illustrating an example of an encoded string to which an encoder in Fig. 11 is output. Fig. 18 is a block diagram illustrating a functional 30 configuration example of the encoder. Fig. 19 is a flowchart describing of encoding processing. 18 SP248477WO03 Fig. 20 is a block diagram illustrating a functional configuration example of a decoder. Fig. 21 is a flowchart describing a decoding process. Fig. 22 is a flowchart describing an encoding process. 5 Fig. 23 is a flowchart describing a decoding process. Fig. 24 is a flowchart describing an encoding process. Fig. 25 is a flowchart describing an encoding process. Fig. 26 is a flowchart describing an encoding process. Fig. 27 is a flowchart describing an encoding process. 10 Fig. 28 is a view illustrating a configuration example of a coefficient learning apparatus. Fig. 29 is a flowchart describing a coefficient learning process. Fig. 30 is a diagram illustrating a coefficient table. 15 Fig. 31 is a diagram illustrating the extension of a coefficient table. Fig. 32 is a diagram illustrating the reduction of a coefficient table. Fig. 33 is a block diagram illustrating a functional 20 configuration example of an encoder. Fig. 34 is a flowchart describing an encoding process. Fig. 35 is a block diagram illustrating a functional configuration example of a decoder. Fig. 36 is a flowchart describing a decoding process. 25 Fig. 37 is a diagram illustrating the sharing of a coefficient table using blended learning. Fig. 38 is a view illustrating a configuration example of a coefficient learning apparatus. Fig. 39 is a flowchart describing a coefficient learning 30 process. Fig. 40 is a. block diagram illustrating a configuration 19 SP248477WO03 example of hardware of a computer executing a process to which the present invention is applied by a program. MODE FOR CARRYING OUT THE INVENTION [0041] An embodiment of the present invention will be described with reference to the drawings. In addition, the description thereof is performed in the following sequence. 1. First embodiment (when the present invention is 10 applied to a frequency band expansion apparatus) 2. Second embodiment (when the present invention is applied to an encoder and a decoder) 3. Thirdembodiment (when a coefficient index is included in high band encoded data) 15 4. Fourth embodiment (when a difference between coefficient index and a pseudo high band sub-band power is included in high band encoded data) 5. Fifth embodiment (when a coefficient index is selected using an estimation value). 20 6. Sixth embodiment (when a portion of a coefficient is :o eons) 7. Seventh Embodiment (In Case Where Coefficient Table is Extended or Reduced) 8. Eighth Embodiment (In Case Where Learning is Performed 25 Using Broadband Instruction Signals Having Different Conditions) [0042] <1. First Embodiment> Ina first embodiment, a process that expands a frequency 30 band (hereinafter, referred to as a frequency band expansion process) is performed with respect to a signal component of 20 SP248477WO03 a low band after decoding obtained by decoding encoded data using a high cancelation encoding method. [0043] [Functional Configuration Example of Frequency Band Expansion Apparatus] Fig. 3 illustrates a functional configuration example of a frequency band expansion apparatus according to the present invention. [0044] 10 A frequency band expansion apparatus 10 performs a frequency band expansion process with respect to the input signal by setting a signal component of the low band after decoding as the input signal and outputs the signal after the frequency band expansion process obtained by the result as 15 an output signal. [0045] The frequency band expansion apparatus 10 includes a low-pass filter 11, a delay circuit 12 , a band pass filter 13, a characteristic amount calculation circuit 14, a high 20 band sub-band power estimation circuit 15 , a high band signal production circuit 16, a high-pass filter 17 and a signal adder 18. [0046] The low-pass filter 11 filters an input signal by a 25 predetermined cut off frequency and supplies a low band signal component, which is a signal component of the low band as a. signal after filtering to the delay circuit 12. [0047] Since the delay circuit 12 is synchronized when adding 30 the low band signal component from the low-pass filter 11 and a high band signal component which will be described later 21 SP248477W003 to each other, it delays the low signal component only a certain time and the low signal component is supplied to the signal adder 18. [0048] 5 The band pass filter 13 includes band pass filters 13-1 to 13-N having pass bands different from each other. The band pass filter 13-i(