JPH0711757B2 - Portable musical instruments - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a portable musical instrument such as a portable electric musical instrument and a portable electronic musical instrument, and more particularly to a portable musical instrument capable of generating deep bass.

The above-mentioned portable musical instrument refers to a small musical instrument which has a shape or size suitable for portable performance and is easy to carry.

[Prior Art] As a conventional portable musical instrument, a so-called electric musical instrument or electronic musical instrument having an acoustic device for electrically amplifying and producing a musical sound and having a configuration suitable for carrying is known.

[Problems to be Solved by the Invention] By the way, in such a portable musical instrument, the main body is required to be small to some extent in terms of its portability and ease of standing, and the small-sized main body has a small aperture. The speaker unit of is arranged. For this reason, the conventional portable musical instrument has a disadvantage that it can generate only a poor sound with no bass. There are also known types of portable musical instruments that have a resonator inside to produce low frequencies, but with these types of musical instruments, the main body is similar to an acoustic guitar when trying to obtain sufficient sound quality. There is a disadvantage in that sufficient sound quality cannot be obtained when the size is increased and the size is not suitable for standing, but when the size is suitable for standing.

In view of the drawbacks of the conventional example, an object of the present invention is to realize a portable musical instrument which has a size suitable for being carried and which produces deep bass.

[Means for Solving the Problem] In order to achieve the above object, according to the present invention, a portable musical instrument main body is provided with a resonator including a cavity and an acoustic mass means, and a part of the resonator. A vibrator having a vibrating body that drives the resonator on one side, and a vibration that drives the vibrator so as to cancel the action of the resonator on the diaphragm of the vibrator when the sounding device is driven. By arranging the resonator driving means, the resonance of the resonator is more positively utilized.

[Operation] A conventional portable musical instrument audio device includes a speaker system,
This speaker system is composed of a power amplifier that drives a so-called constant voltage and has an output impedance of substantially zero. Therefore, in these musical instruments, the output sound pressure characteristic is affected by the volume of the cavity behind the diaphragm of the speaker unit, and if the volume of the cavity is reduced in order to downsize the resonator and the instrument body, the bass characteristic is impaired. was there.

In the present invention, the driving means drives the vibrator so as to cancel the action of the vibrator from the resonator (cavity) side. That is, the vibrator is driven in a so-called dead state in which it is sufficiently damped without being affected by the action from the resonator side. Therefore, the frequency characteristic of the direct radiation sound is not affected by the volume of the space behind the direct radiation surface of the vibrator, and the volume of this space is as a cavity of the resonator.
In addition, the size can be reduced as long as no inconvenience occurs as a container of the vibrator. When viewed from the resonator side, driving the vibrator so as to cancel the atmospheric action from the resonator side when driving the resonator means that the diaphragm of the vibrator cannot be driven from the resonator side. It means that it has become a wall. Therefore, the Q value of the resonator is not affected by the characteristics (f _O , Q _O ) of the vibrator, and a sufficiently high Q value can be secured even if the resonance frequency is lowered. This allows
Even if the cavity, and hence the instrument body, is downsized, a sufficient level of deep bass sound (resonance sound) can be generated from the resonator.

[Effects] As described above, according to the present invention, even though the speaker unit having a small diameter is arranged in the small instrument main body, the resonance of the resonator in the main body is positively utilized to achieve sufficient bass characteristics. You can get excellent sound quality. Moreover, if the present invention is applied to a portable musical instrument such as an acoustic guitar, the cavity of the resonator can be downsized without impairing the sound quality,
The instrument body can be further miniaturized to an extent suitable for standing.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the basic construction of a portable electric musical instrument according to an embodiment of the present invention. The electric musical instrument shown in the same figure is one in which the present invention is applied to a musical instrument in which a sounding device 2 such as a drum film, a string of a guitar or a lead, or a reed is arranged on the left side of a musical instrument casing 1 also serving as a resonator. A hole is made in the upper surface of the body 1 and a vibrator (dynamic speaker unit) 4 having a diaphragm 3 is attached,
A sealed box 5 having the upper surface of the musical instrument housing 1 as one surface is formed on the rear surface of the vibrator 4, and the inside of the sealed box 5 is acoustically connected to the outside of the musical instrument housing 1 on the upper surface of the musical instrument housing 1. A duct 6 is provided to form a Helmholtz resonator by the closed box 5 and the duct 6, and a sounding circuit 7 such as a pickup for converting mechanical or acoustic vibration of the sounding device 2 into an electric signal and the sounding circuit 7 A vibrator drive circuit 8 for driving the vibrator 4 based on the supplied electric signal is provided.

In the Helmholtz resonator, an air resonance phenomenon occurs due to the air spring in the closed box 5 which is a closed cavity and the air mass in the duct 6.

And this resonance frequency f _OP is Can be asked as Here, V ₁ is the volume of the closed box 5, S ₁ is the cross-sectional area of the duct 6, l ₁ is the length of the duct 6, and c is the speed of sound.

The Helmholtz resonator and the vibrator 4 constitute a speaker system (hereinafter referred to as a speaker system with a resonance port) which is similar in shape to a conventional phase inversion (bass reflex) speaker system.

The vibrator drive circuit 8 is configured to drive the Helmholtz resonator, that is, the closed box (cavity) 5 when the Helmholtz resonator is driven.
The vibrator 4 is driven so as to cancel the atmospheric action from the side. Such drive devices, equivalently detect and enter some way a motional signal corresponding to the movement of the negative impedance generator or vibrator for generating a negative impedance component (-Z _O) in the output impedance A known circuit such as a motional feedback (MFB) circuit that negatively feeds back to the side can be applied.

Next, the operation of the portable electric musical instrument shown in FIG. 1 will be described.

When the sounding device 2 is operated during the performance of this electric musical instrument, the sounding circuit 7 converts mechanical or acoustic vibration in the sounding device 2 into an electric signal. The vibrator driving circuit 8 drives the vibrator 4 based on the electric signal supplied from the sounding circuit 7. As a result, the mechanical vibration of the sounding device 2 is directly pronounced, and at the same time, the sound is amplified through the speaker system with the resonance port including the vibrator 4 and the Helmholtz resonator.

In this portable electric musical instrument, since the musical instrument casing 1 is a resonance box, the musical instrument is tuned even when the sound generation circuit 7 and the vibrator drive circuit 8 are turned off, and the performer himself / herself can play the contents of the performance. You can generate enough volume to check.

When a drive signal is applied from the vibrator drive circuit 8 to the vibrator 4, the vibrator 4 electromechanically converts the drive signal to drive the diaphragm 3 back and forth (up and down in the figure). The diaphragm 3 converts this reciprocating motion into mechanical sound. Here, the front surface side (upper surface side in the figure) of the diaphragm 3 forms a direct radiating portion for directly radiating sound to the outside, and the rear surface side of the diaphragm 3 (lower surface side in the figure).
Represents a resonator driving unit for driving the Helmholtz resonator composed of the closed box 5 and the duct 6. And
On the rear surface side of the vibration plate 3, an atmospheric reaction against the action of the vibration plate is applied from the air in the closed box 5, but the vibrator drive circuit 8 drives the vibrator 4 so as to cancel this atmospheric reaction.

Thus, when the vibrator 4 is driven so as to cancel the atmospheric reaction from the resonator when the Helmholtz resonator is driven, the diaphragm 3 cannot be driven from the resonator side, and when viewed from the resonator side, Acts as a rigid body or wall. Therefore, the resonance frequency and Q as the Helmholtz resonator are independent of the resonance frequency and Q as the direct radiation portion by the diaphragm 3 and the vibrator 4, and the resonator driving energy from the vibrator 4 is also directly radiated as described above. It will be given independently of the department. Further, the vibrator 4 is not affected by the atmospheric reaction from the resonator, that is, the closed box 5 side,
Since it is driven in a so-called dead state, the frequency characteristic of the direct radiation sound is not influenced by the volume of the closed box 5. Therefore, according to the configuration of this embodiment, the volume of the closed box 5 which is the cavity of the Helmholtz resonator is made smaller than that of a portable electric musical instrument such as a conventional acoustic guitar, and the resonance frequency f _OP is set to be lower than that of the conventional musical instrument. However, the Q value can be set to a sufficiently large value. As a result, the first
In the portable electric musical instrument shown in the figure, even if the sealed box 5 is made much smaller than the conventional portable electric musical instrument, it is possible to reproduce even lower frequencies.

In FIG. 1, a vibrator 4 drives a diaphragm 3 in response to a drive signal from a vibrator drive circuit 8 and drives a Helmholtz resonator composed of a sealed box 5 and a duct 6 independently. Give energy. As a result, sound is directly radiated from the diaphragm 3 as indicated by the arrow a in FIG. 1, and the air in the closed box 5 is caused to resonate, as indicated by the arrow b in FIG. Sound of sufficient sound pressure is resonantly radiated from the resonant radiating portion (opening port 9 of the duct 6). Then, by adjusting the air equivalent mass in the duct 6 in the Helmholtz resonator, the resonance frequency f _{OP is set} to the vibrator 4
2 is set lower than the reproduction frequency band and the Q value is set to an appropriate level by adjusting the equivalent resistance of the duct 6, under the condition that an appropriate level of sound pressure is obtained from the duct 6, for example, as shown in FIG. The frequency characteristic of the sound pressure as shown can be obtained. In the figure, a shows the frequency characteristic of the sound pressure directly radiated from the vibrator 4, and b shows the opening port 9
The frequency characteristic of the resonance radiation acoustic sound pressure from is shown.

FIG. 3 shows a specific example of the portable electric musical instrument of FIG. The electric musical instrument shown in FIG. 3 is an example in which a small-diameter speaker unit is used in a so-called semi-acoustic guitar which is thinner than a conventional acoustic guitar. In this portable electric musical instrument, a sealed box 5 is formed by partitioning a part of a guitar sound body (instrument housing) 1, and a hole is formed in a part of the front plate 11 of the sound body 1 which forms one surface of the sealed box 5. The speaker unit (vibrator) 4 is attached to the speaker box, and a duct 6 that cooperates with the closed box 5 to form a Helmholtz resonator is provided. Further, a pickup (sounding circuit) 7 for converting the vibration of the guitar string (sound generating device) 2 into an electric signal and a negative impedance generating circuit (vibrator driving device) 8 for driving the speaker unit 4 are provided. .

In the figure, 12 is a sound hole, 13 is a tail piece, 14 is a neck, and 15 is a piece.

As described above, by using a part of the reverberation drum 1 of the conventional semi-acoustic guitar as a resonator of the speaker system and driving this speaker system with negative impedance, the bass characteristics of the speaker unit 4 are irrelevant regardless of the characteristics of the speaker unit 4. Extended frequency characteristics can be obtained.

FIG. 4 shows the basic structure of a portable electronic musical instrument according to another embodiment of the present invention. In the electronic musical instrument shown in the figure, the entire interior of the musical instrument casing 1 is shared as a closed box 5, and the sound producing control device comprising the sound producing device 2 and the sound producing circuit 7 shown in FIG. The configuration is the same as that of FIG. 1 except that it is composed of a sound production instructing means 2 such as a pad and a breathing air input device, and a musical sound forming means 7 for electrically forming a musical sound instructed by the sound producing instruction means 2. Has been done.

Therefore, the musical tone signal at the time of performance is formed in an electric circuit such as a memory or an oscillator, the sound source does not directly generate mechanical or acoustic vibration, and the musical instrument casing does not directly generate vibration. Since it does not resonate, there is no musical sound when the power is off.
Works the same as the instrument shown.

The embodiment of FIG. 4 can be applied to portable electronic musical instruments such as portable electronic keyboards, electronic percussion instruments, electronic wind instruments, etc. According to this embodiment, a relatively small space allowed for these portable electronic musical instruments. Can be used to improve the bass characteristic.

Next, the operation of the acoustic device that drives the speaker system using the Helmholtz resonator by the negative impedance generation circuit will be described.

FIG. 5 is a vibrator drive circuit 8 shown in FIGS. 1 and 3.
2 shows an electrical equivalent circuit of a portion consisting of a vibrator system, a closed box 5, and a speaker system with a resonance port, which is composed of a duct 6. Here, E _O represents a voltage source that is a drive signal source. The parallel resonance circuit Z ₁ is based on the equivalent motional impedance of the vibrator 4, r _O is the equivalent resistance of the drive system, S _O is the equivalent stiffness of the vibration system, and m _O is the equivalent mass of the vibration system. There is. The series resonance circuit Z ₂ is based on the equivalent motional impedance of the Helmholtz resonator constituted by the duct 6 and the closed box (cavity) 5, r _C is the equivalent resistance of the cavity 5, and S _C is the cavity 5. Is the equivalent stiffness, r _P is the equivalent resistance of the duct 6, and m _P is the equivalent mass of the duct 6. A is a force factor, when the vibrator 4 is dynamic conductivity type direct radiation speaker, the A = Bl _V a B magnetic flux density in the magnetic gap, when a conductor the entire length of the l _V voice coil. Further, Z _V in the figure is the internal impedance (non-motional impedance) of the vibrator 4,
Is a direct-radiation speaker unit of electrodynamic type, it is mainly the resistance R _{V of the} voice coil and contains a small amount of inductance.

FIG. 6 is an electrical equivalent circuit when Z _V −Z _O = 0 in FIG. 5, that is, the internal impedance (non-motional impedance) of the vibrator 4 is equivalently completely nullified. Here, the coefficient attached to the value of each element is omitted.

The following is clear from this equivalent circuit.

First, the parallel resonance circuit Z ₁ having the equivalent motional impedance of the vibrator 4 is AC short-circuited with zero impedance at both ends. Therefore, this parallel resonant circuit Z ₁
Has a Q value of 0 and is virtually no longer a resonant circuit. That is, in this vibrator 4,
The concept of the lowest resonance frequency, which simply had a Helmholtz resonator with the oscillator 4 attached, is no longer present. Hereinafter, when the amount equivalent to the minimum resonance frequency f _O of the vibrator 4 is referred to, the above concept that has been substantially invalidated is merely called. As described above, as a result of the unit resonance system (parallel resonance circuit) Z ₁ being substantially not a resonance circuit, the Helmholtz resonance system (series resonance circuit) Z _{2 is the} only resonance system in this acoustic device.

Further, as a result of the vibration system being substantially a resonance circuit, the vibrator 4 linearly responds in real time to the drive signal input, and does not make a transient response at all. Signal E _O ) is faithfully electromechanically converted,
The diaphragm 3 will be displaced. That is, it is a complete braking state (so-called speaker dead state). In this state, the direct radiation output sound pressure frequency characteristic near the minimum resonance frequency f _O equivalent value of this speaker unit is 6 dB / oct. On the other hand, the characteristic of the normal voltage drive state is 12 dB.
It becomes / oct.

On the other hand, since the series resonance circuit Z ₂ based on the equivalent motional impedance of the Helmholtz resonator is connected to the drive signal source E _O with zero impedance, there is no mutual dependence relationship with the parallel resonance circuit Z _1. , Parallel resonant circuit
Z ₁ and the series resonant circuit Z ₂ will coexist independently and independently. Therefore, the volume of the closed box 5 (inversely proportional to S _C ) and the shape and size of the duct 6 (proportional to m _P ) do not affect the direct radiation characteristics of the vibrator 4, and the resonance frequency of the Helmholtz resonator is The f _CP and the Q value Q _CP are not affected by the equivalent motional impedance of the vibrator 4. That is, the characteristic value of the Helmholtz resonator and the characteristic value of the vibrator 4 can be set independently. Further, since the series resistance of the series resonance circuit Z ₂ is only r _C + r _P , and these are usually sufficiently small values, the Q value of the series resonance circuit Z ₂ , that is, the Helmholtz resonator is set to be sufficiently high. can do.

From another point of view, the unit vibration system is not actually a resonance system, so it is displaced according to the drive signal input,
It is substantially unaffected by external forces, especially atmospheric reaction due to the equivalent stiffness S _C of the closed box 5. Therefore, the diaphragm 3 of the vibrator 4 is equivalently a wall when viewed from the closed box 5 side, and the existence of the vibrator 4 when viewed from the Helmholtz resonator is nullified. Therefore, the resonance frequency and the Q value as the Helmholtz resonator do not depend on the non-motional impedance of the vibrator 4, and the resonance frequency is set to a frequency at which the Q value of the resonance becomes very small in the usual driving method. Also in the case of performing, the Q value can be maintained at a sufficiently large value. Further, the Helmholtz resonance system is a virtual speaker that emits acoustic waves completely independently of the unit drive system. Even though this virtual speaker is realized with a small diameter corresponding to the port diameter, it is equivalent to an extremely large diameter speaker unit as an actual speaker unit in view of its bass reproduction capability.

Comparing the above with a conventional system in which a speaker system with a bass reflex type or a resonator as used in the acoustic guitar is driven by a normal power amplifier, in the conventional system, as is well known, the unit vibration system Z ₁ And a Helmholtz resonance system Z ₂ exist, and the resonance frequency and Q value of each resonance system are closely dependent on each other. For example, if the duct 6 is made longer or thinner (m _P becomes larger) in order to lower the resonance frequency of the Helmholtz resonance system Z ₂ , the unit vibration system Z ₁ has a higher Q value and the Helmholtz resonance system Z ₂ has the same. It becomes low and it is a closed box (empty) 5
To reduce the volume and (S _C increases), or a longer duct 6, thinned even kept constant resonance frequency of the Helmholtz resonance system Z _2, the unit vibration system Z ₁ the Q value and resonance The frequency became higher and the Q value was further lower in the Helmholtz resonance system Z ₂ . That is, since the output sound pressure frequency characteristics of the speaker system are closely related to the characteristics of the speaker unit 4, the volume of the cavity 5 and the dimensions of the duct 6, a sophisticated design technique is required to match them. there were. Further, even if they are perfectly matched, the low frequency limit of uniform reproduction is high at the resonance frequency f _{OC when} the speaker unit 4 is attached to the cavity 5. Once matched, the sound reproduction band of the existing system can be simplified without reducing the size of the cavity 5 without impairing the output sound pressure characteristics, especially the low-frequency characteristics, and without impairing the characteristics such as sound quality. It was generally considered impossible to expand to. Also, the above Helmholtz resonance system Z ₂
The relationship between the frequency in the band lower than the resonance frequency f _OP and the resonant acoustic radiation ability is, when viewed from the sound pressure level, decreased at a rate of about 12 dB / oct with respect to the decrease in the frequency, and the resonance frequency is the bass reflex type. Alternatively, if it is set extremely low with respect to the basic idea of the speaker system with a resonator, it becomes extremely difficult to correct it by increasing or decreasing the input signal level.

As described above, the drive device of this embodiment is designed to drive the speaker system utilizing Helmholtz resonance by negative impedance, so that the unit drive system of the system and the characteristics and dimensions of the Helmholtz resonance system can be set independently.
Moreover, even if the resonance frequency of the Helmholtz resonance system is set low, the Q value and bass reproduction ability can be kept high, and the unit drive system has a strong resonator drive ability (6d
B / oct), it is possible to obtain a characteristic that the waviness of the frequency characteristic can be corrected by increasing / decreasing the input signal level, for example, increasing / decreasing the normal sound quality adjustment degree. Further, as a result of the unit vibration system being substantially no resonance system, there is no abrupt phase change in the vicinity of the frequency f _OC , and the phase characteristics are good.
Therefore, the cavity 5 can be miniaturized without deteriorating the frequency characteristics and the sound quality, and the speaker system can be configured in a small size, and the sound quality can be improved as compared with the conventional speaker system driven by a constant voltage, or It is possible to easily expand and drive the sound reproduction band, particularly the low-pitched sound side.

In the above description, only the case where Z _V −Z _O = 0 is described, but when Z _V −Z _O > 0, the characteristic values of the unit vibration system and the Helmholtz resonance system are
Depending on the value of Z _V -Z _O becomes a value between the case of the Z _V -Z _O = 0 if the conventional constant voltage drive system. Therefore, positively utilizing this property, for example, the Q value of the Helmholtz resonance system is adjusted by adjusting the port diameter or inserting a mechanical Q damper such as glass wool or felt in the cavity 5. Alternatively, it is possible to perform by adjusting the negative impedance -Z _O.

FIG. 7 shows a basic configuration of a negative impedance generating circuit 8 for driving the vibrator (speaker unit) 4 with a negative impedance.

The circuit shown in the figure applies the output of the amplifier 81 having a gain A to the load Z _L by the vibrator 4. Then, the current flowing through the load Z _L I _L
Of the transmission gain β and the amplification circuit 81
Give positive feedback to. In this way, the output impedance Z _{O of the} circuit is obtained as Z _O = Z _S (1−Aβ) ... (2). If Aβ> 1 from this equation (2),
Z _O is an open stable negative impedance. here,
Z _S is the impedance of the sensor that detects the current.

Therefore, in the circuit of FIG. 7, a desired negative impedance component can be included in the output impedance by appropriately selecting the type of impedance Z _S. For example, in the case of detecting the current I _L by the voltage across the impedance Z _S is the impedance Z _S is the resistance R _S
Then, the negative impedance component becomes a negative resistance component, the inductance L _S becomes a negative inductance component, and the capacitance C _S becomes a negative capacitance. Further, the integrator used in the feedback circuit 83, the impedance Z _S negative impedance component by detecting and integrating the voltage across the inductance L _S of the can is referred to as negative resistance component, further in the feedback circuit 83 using differentiator, negative impedance component be detected by differentiating the voltage across the capacitance C _S as the impedance Z _S becomes a negative resistance component. As the current detection sensor, it is possible to use a current probe such as a CT or a Hall element in addition to the impedance elements R _S , L _S , and C _S.

A concrete example corresponding to such a circuit is, for example, Japanese Patent Publication No. 59-
No. 51771 is shown.

It is also possible to detect the current on the non-grounded side of the vibrator 4. A concrete example of such a circuit is, for example, Japanese Patent Publication No.
-83704 and the like. FIG. 8 shows an example of BTL connection, but it is easy to apply it to the circuit of FIG. 8th
Reference numeral 84 in the figure is an inverting circuit.

FIG. 9 shows a specific circuit example of an amplifier including a negative resistance component in the output impedance.

The output impedance Z _O in the amplifier of FIG. 9 is Z _O = R _S (1-Rb / Ra) = 0.22 (1-30 / 1.6) = -3.9 (Ω).

[Other Embodiments] The present invention is not limited to the above embodiments,
It can be appropriately modified and implemented. For example, in the above-mentioned embodiment, the duct having the opening port is used as the acoustic mass means for constructing the resonator, but this may be a passive vibrating body such as a simple opening or a drone cone.

Further, in the above-described embodiment, the case where the negative impedance generating circuit is mainly used as the driving means has been described, but this driving means drives the vibrating body of the vibrator so as to cancel the reaction from the surroundings. As long as it is a so-called MFB as disclosed in JP-B-58-81156.
It may be a circuit.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of a portable electric musical instrument according to an embodiment of the present invention, FIG. 2 is an explanatory diagram of an output sound pressure frequency characteristic of an audio device of the musical instrument of FIG. 1, and FIG. ) (B) is a block diagram of a concrete application example of the portable electric musical instrument of FIG. 1, (a) is a front view, (b) is II-II.
FIG. 4 is a sectional view, FIG. 4 is a basic configuration diagram of a portable electronic musical instrument according to another embodiment of the present invention, and FIG. 5 is an electrical equivalent circuit diagram of an audio device portion of the musical instrument of FIGS. FIG. 6 is an equivalent circuit diagram when Z _V −Z _O = 0 in FIG. 5, FIG. 7 is a basic circuit diagram of a circuit for generating negative impedance, and FIG. 8 is FIG. FIG. 9 is a circuit diagram showing a modified example of the circuit of FIG. 7, and FIG. 9 is a circuit diagram showing a concrete example of the circuit of FIG. 1: Instrument housing 2: Sounding device (guitar strings, sounding indication means) 3: Vibrating plate 4: Vibrator (speaker unit) 5: Closed box (cavity of resonator) 6: Duct 7: Sounding circuit (pickup, musical sound) Forming circuit) 8: Vibration drive 9: Opening port

Claims (1)

[Claims] 1. A sounding control device for generating a musical sound wave-shaped electric signal according to a performance operation, and an audio device for converting the electric signal into a sound to be sounded are housed in a musical instrument body suitable for carrying. In a portable musical instrument, the acoustic device comprises a cavity and a resonator comprising acoustic mass means for acoustically connecting the cavity to an external region, and one surface provided on an outer wall of a box forming the cavity. A vibrator having a vibrating body for driving the resonator, and a vibrating means for driving the vibrating body so as to cancel the action of the resonator on the vibrating body when the resonator is driven. A portable musical instrument characterized by.