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ing companies, for all graduations of the ordinary floor slopes required, both for direct and reverse slopes. The variation is made in the rear leg of the standard in order to retain the correct height of the seat edge under all conditions. (The construction of theatre chairs describing different types, coverings, and so forth, will be discussed later.)

Sometimes it will be necessary to compensate for the higher rate of rise at the 'last few rows, to install level platforms in front of the seats for the patrons, comfort thus providing a rest for their feet. These platforms should be installed when the difference in elevation between any two consecutive rows exceeds 3 inches. (See Figure 18.) When these platforms are installed, it will be necessary to provide a ramp from the level platform to meet the slope of the aisle. (See Figure 19.)

Aisles

The usual number of seats permitted between aisles is fourteen, and seven betWeen a wall and aisle. This number varies, however, with the different local and state codes, which in some instances permit only ten seats between aisles. Some codes specify the maximum number of seats necessary to pass to reach an aisle, and in one instance Where this number is specified as six, the interpretation was that only thirteen seats were permissible in the center bank and six in the side banks.

The regulations are so varied in regard to seating installations in different localities that the inexperienced designer should consult with 9. representative of the seat manufacturer who will furnish this equipment, as he will be very helpful and fully cognizant of all the related problems.

The next step in the seating layout is the determination of the required aisle widths and their locations. The location of the aisles is governed by the regu

lations referred to in the preceding paragraph, but in some cases it might prove advantageous to use fewer seats in the center bank and more in the side banks, using side aisles along the exterior walls. The proper layout is governed by the total clear width of the theatre, the size of the chairs to be generally used, and the required width of the aisles.

Most codes determine the Width of the aisles by stating a minimum clearance at the front row with a certain increase in width for each foot of length of the aisle such as 1/2 inch to 5 feet.

The aisle width will be measured at right angles to the aisle and between the seat arms. Since each seat row is set to a different radius, it will be found that the angle of the seat arm with the aisle line will vary. This angle will be greatest at the first row diminishing towards the back, and on one side of the aisle the clearance line will be determined by the location of the front point of the seat arms, while the line on the opposite side of the aisle will be determined by the location of the rear point of the seat arms. (See Figure 18.)

Cross Aisles

It is sometimes desirable, especially when a cross aisle is involved, to have no variation in the aisle width. It will generally be permitted to make the aisle a clear width for its entire length which will be an average of minimum and maximum requirements.

Cross aisles will be required by the code in some instances when the distance between the first and last rows of seating exceed a certain figure. Alt may be required, at times, to extend these aisles through all banks of seats but in other cases the cross aisle is not required through the center bank, but only through the tw0 side banks.

If cross aisles are used they should lead directly to the emergency exits.

Depression for Carpets

The aisles should be depressed for the installation of carpet and padding. This depression should be 5/8 inches with carpet strips and tooled edges. (See Figure 13.) Depressions for carpet in the aisles and elsewhere in the theatre saves wear and tear on the edges of the carpet, provides for more secure fastening of the carpet, and is less of a hazard to patrons emerging from their seats to the aisles. .

The width of the carpet depressions should be at least 5 inches less than the clear aisle width as determined in accordance with the preceding paragraph. Should this resulting width at the widest part of the aisle only be 2 or 3 inches more than a multiple of 27 inches (the Width of three-quarter carpet, then the Width of the depression should be reduced to save cutting and sewing in the carpet installation, and the yardage of carpet.

The 5-inch differential, however, will allow for certain errors in the layout and the actual construction and installation of the seats, and will prevent the necessity of drilling holes for the seat standards too close to the carpet depression with the resulting cracking and chipping of the floor or the projection of the seat standards over the carpet.

Acoustical Treatment

Although it is recommended that the required acoustical correction necessary in the auditorium be checked by an acous 'tical engineer whose experience covers

reproduced and amplified sound problems, we will outline herewith the general method of determining the amount and location of such material.

First, the optimal reverberation time of the auditorium, which is independent on the total volume, Will have to be determined. Direct reacting tables giving the different values of the reverberation time for definite volumes are available, but the formula used is

t = .05V/As,

Where t is the reverberation time, V is the volume, and As is the number of absorption units required, but it is first necessary to figure the number of absorption units provided in the auditorium by the contents, such as seats, carpets, draperies, and occupants. These amounts will have to be more or less assumed but the following method has been found very satisfactory.

Find the natural absorption on account of room volume from Table 1, or from the formula,

A = .29V2/3

Next, assume one-third of the seats occupied with a coefficient of 4.7 each, two-thirds of the seats unoccupied with a coefiicient of 2.3 each, carpet with a cofficient of 0.40 to the square foot, drapes with a coefiicient of 0.60 to the square foot. The sum of these units, less the required number of units as derived from the formula t = .05V/As will give the number of units which will need to be supplied by acoustical treatment, using a material whose average cofficient .60 to the square foot in the range between 128 and 4,096 cycles.

It is not necessary to take into consideration the noise coefiicient as generally given for tested materials.

As previously pointed out, although

THEATRE CATALOG 1947-43

# 1947-48 Theatre Catalog, 6th Edition, Page 156 (144)

## 1947-48 Theatre Catalog, 6th Edition, Page 156

FIGURE 18-Sometimes it will be necessary to compensate for the higher rate of rise at the last few rows, to install level platforms in front of the seats for the patrons' comfort, thus providing a rest for their feet. These platforms should be installed when the difference in elevation between any two rows exceeds 3 inches. The drawing shows how such steppings and seat positions are generally arranged.ing companies, for all graduations of the ordinary floor slopes required, both for direct and reverse slopes. The variation is made in the rear leg of the standard in order to retain the correct height of the seat edge under all conditions. (The construction of theatre chairs describing different types, coverings, and so forth, will be discussed later.)

Sometimes it will be necessary to compensate for the higher rate of rise at the 'last few rows, to install level platforms in front of the seats for the patrons, comfort thus providing a rest for their feet. These platforms should be installed when the difference in elevation between any two consecutive rows exceeds 3 inches. (See Figure 18.) When these platforms are installed, it will be necessary to provide a ramp from the level platform to meet the slope of the aisle. (See Figure 19.)

Aisles

The usual number of seats permitted between aisles is fourteen, and seven betWeen a wall and aisle. This number varies, however, with the different local and state codes, which in some instances permit only ten seats between aisles. Some codes specify the maximum number of seats necessary to pass to reach an aisle, and in one instance Where this number is specified as six, the interpretation was that only thirteen seats were permissible in the center bank and six in the side banks.

The regulations are so varied in regard to seating installations in different localities that the inexperienced designer should consult with 9. representative of the seat manufacturer who will furnish this equipment, as he will be very helpful and fully cognizant of all the related problems.

The next step in the seating layout is the determination of the required aisle widths and their locations. The location of the aisles is governed by the regu

lations referred to in the preceding paragraph, but in some cases it might prove advantageous to use fewer seats in the center bank and more in the side banks, using side aisles along the exterior walls. The proper layout is governed by the total clear width of the theatre, the size of the chairs to be generally used, and the required width of the aisles.

Most codes determine the Width of the aisles by stating a minimum clearance at the front row with a certain increase in width for each foot of length of the aisle such as 1/2 inch to 5 feet.

The aisle width will be measured at right angles to the aisle and between the seat arms. Since each seat row is set to a different radius, it will be found that the angle of the seat arm with the aisle line will vary. This angle will be greatest at the first row diminishing towards the back, and on one side of the aisle the clearance line will be determined by the location of the front point of the seat arms, while the line on the opposite side of the aisle will be determined by the location of the rear point of the seat arms. (See Figure 18.)

Cross Aisles

It is sometimes desirable, especially when a cross aisle is involved, to have no variation in the aisle width. It will generally be permitted to make the aisle a clear width for its entire length which will be an average of minimum and maximum requirements.

Cross aisles will be required by the code in some instances when the distance between the first and last rows of seating exceed a certain figure. Alt may be required, at times, to extend these aisles through all banks of seats but in other cases the cross aisle is not required through the center bank, but only through the tw0 side banks.

If cross aisles are used they should lead directly to the emergency exits.

Depression for Carpets

The aisles should be depressed for the installation of carpet and padding. This depression should be 5/8 inches with carpet strips and tooled edges. (See Figure 13.) Depressions for carpet in the aisles and elsewhere in the theatre saves wear and tear on the edges of the carpet, provides for more secure fastening of the carpet, and is less of a hazard to patrons emerging from their seats to the aisles. .

The width of the carpet depressions should be at least 5 inches less than the clear aisle width as determined in accordance with the preceding paragraph. Should this resulting width at the widest part of the aisle only be 2 or 3 inches more than a multiple of 27 inches (the Width of three-quarter carpet, then the Width of the depression should be reduced to save cutting and sewing in the carpet installation, and the yardage of carpet.

The 5-inch differential, however, will allow for certain errors in the layout and the actual construction and installation of the seats, and will prevent the necessity of drilling holes for the seat standards too close to the carpet depression with the resulting cracking and chipping of the floor or the projection of the seat standards over the carpet.

Acoustical Treatment

Although it is recommended that the required acoustical correction necessary in the auditorium be checked by an acous 'tical engineer whose experience covers

reproduced and amplified sound problems, we will outline herewith the general method of determining the amount and location of such material.

First, the optimal reverberation time of the auditorium, which is independent on the total volume, Will have to be determined. Direct reacting tables giving the different values of the reverberation time for definite volumes are available, but the formula used is

t = .05V/As,

Where t is the reverberation time, V is the volume, and As is the number of absorption units required, but it is first necessary to figure the number of absorption units provided in the auditorium by the contents, such as seats, carpets, draperies, and occupants. These amounts will have to be more or less assumed but the following method has been found very satisfactory.

Find the natural absorption on account of room volume from Table 1, or from the formula,

A = .29V2/3

Next, assume one-third of the seats occupied with a coefficient of 4.7 each, two-thirds of the seats unoccupied with a coefiicient of 2.3 each, carpet with a cofficient of 0.40 to the square foot, drapes with a coefiicient of 0.60 to the square foot. The sum of these units, less the required number of units as derived from the formula t = .05V/As will give the number of units which will need to be supplied by acoustical treatment, using a material whose average cofficient .60 to the square foot in the range between 128 and 4,096 cycles.

It is not necessary to take into consideration the noise coefiicient as generally given for tested materials.

As previously pointed out, although

THEATRE CATALOG 1947-43