自由场法测量声功率.doc

实验四 自由场法测量声功率
一、 实验目的

掌握半消声室精密法测声功率的原理和方法。

二、 实验要求
1. 在消声室采用半球面作为测量表面。
2. 每个测点测量1次。
三、 实验环境
1．半消声室
2．噪声源（以320W大宇6060T手电钻为例）
3．HS6288B声级计（2型）
4．1／2吋传声器延长电缆
5．传声器支架
四、 实验内容、步骤
1. 实验内容：测量电钻空载时的声功率
2. 实验原理：
噪声源的辐射特性通常用指向特性和辐射功率描述。声功率的单位为瓦，如用声功率级表示，则

式中为声源辐射功率，为声功率级（dB）；基准声功率为10－12 W。
3. 指向性声源的声功率测量
将声源放在自由场中，测量出声源周围固定距离处假想球面上许多点的声压级，球的半径应该使测量点位于远场。测量点数目不能太少，测得数值之间的最大变化不得超过6 dB左右，否则必须在更多的点上进行测量。
确定声源的声功率时，将假想球面分成与测点数目相同的面积，传声器测点占有的测试半球的面积相等，用下式求出表面平均声压级：

式中是表面平均声压级；是第i个测点的声压级，N是测点数目。
这时自由场中噪声的声功率为：

式中是测试球面上表面平均声压级,。下面给出以声源为原点测点的直角坐标（x,y,z），z轴选择垂直于水平面向上的方向。
表4.1 测点直角坐标分布如下:
测点号
x/r
y/r
z/r
1
2
3
4
5
6
7
8
9
10
-0.99
0.50
0.50
–0.45
–0.45
0.89
0.33
–0.66
0.33
0
0
-0.86
0.86
0.77
–0.77
0
0.57
0
-0.57
0
0.15
0.15
0.15
0.45
0.45
0.45
0.75
0.75
0.75
0
4. 实验步骤
图4.1 半球面测点布置示意图
将HS自由场传声器装加在HS6288B声级计的延长电缆上并进行校准，在消声室地面中央处画圆确定测量表面的位置，将电钻置于圆心，将传声器夹在支架上，调整支架延伸杆的长度及角度，按图1确定测点位置依次测量各点声压级，按上式计算被测电钻的声功率级。
五、 实验结果
1. 每个测点的原始记录数据：
半球半径 r=0.8m

测点1的记录数据
序号
频率（Hz）
声压级（dB）
1
6.3000000000e+001
4.26850e+001
2
8.0000000000e+001
3.91176e+001
3
1.0000000000e+002
4.49067e+001
4
1.2500000000e+002
4.87235e+001
5
1.6000000000e+002
5.65264e+001
6
2.0000000000e+002
6.03713e+001
7
2.5000000000e+002
5.54823e+001
8
3.1500000000e+002
6.13301e+001
9
4.0000000000e+002
6.27448e+001
10
5.0000000000e+002
5.83394e+001
11
6.3000000000e+002
5.23349e+001
12
8.0000000000e+002
5.74655e+001
13
1.0000000000e+003
6.23429e+001
14
1.2500000000e+003
5.09674e+001
15
1.6000000000e+003
5.11164e+001
16
2.0000000000e+003
5.50970e+001
17
2.5000000000e+003
5.07698e+001
18
3.1500000000e+003
4.81345e+001
19
4.0000000000e+003
5.05024e+001
20
5.0000000000e+003
4.33621e+001
21
6.3000000000e+003
3.89355e+001
22
8.0000000000e+003
3.92586e+001
23
1.0000000000e+004
3.95506e+001
24
1.2500000000e+004
3.59386e+001

测点2的记录数据
序号
频率（Hz）
声压级（dB）
1
6.3000000000e+001
2.85848e+001
2
8.0000000000e+001
3.07662e+001
3
1.0000000000e+002
3.49995e+001
4
1.2500000000e+002
3.67705e+001
5
1.6000000000e+002
4.44302e+001
6
2.0000000000e+002
4.86575e+001
7
2.5000000000e+002
4.85217e+001
8
3.1500000000e+002
6.02939e+001
9
4.0000000000e+002
5.87627e+001
10
5.0000000000e+002
6.10334e+001
11
6.3000000000e+002
6.16746e+001
12
8.0000000000e+002
5.91776e+001
13
1.0000000000e+003
6.38973e+001
14
1.2500000000e+003
6.22307e+001
15
1.6000000000e+003
6.61915e+001
16
2.0000000000e+003
6.68039e+001
17
2.5000000000e+003
7.65683e+001
18
3.1500000000e+003
7.62447e+001
19
4.0000000000e+003
7.22631e+001
20
5.0000000000e+003
6.83699e+001
21
6.3000000000e+003
6.55720e+001
22
8.0000000000e+003
6.60565e+001
23
1.0000000000e+004
6.48718e+001
24
1.2500000000e+004
6.30553e+001

测点3的记录数据
序号
频率（Hz）
声压级（dB）
1
6.3000000000e+001
2.86541e+001
2
8.0000000000e+001
3.17247e+001
3
1.0000000000e+002
4.22254e+001
4
1.2500000000e+002
3.91409e+001
5
1.6000000000e+002
4.55951e+001
6
2.0000000000e+002
4.82254e+001
7
2.5000000000e+002
4.99764e+001
8
3.1500000000e+002
5.81686e+001
9
4.0000000000e+002
5.70080e+001
10
5.0000000000e+002
5.97292e+001
11
6.3000000000e+002
6.09798e+001
12
8.0000000000e+002
6.41925e+001
13
1.0000000000e+003
6.98105e+001
14
1.2500000000e+003
7.22627e+001
15
1.6000000000e+003
7.24525e+001
16
2.0000000000e+003
6.95435e+001
17
2.5000000000e+003
7.46119e+001
18
3.1500000000e+003
6.90675e+001
19
4.0000000000e+003
7.62461e+001
20
5.0000000000e+003
7.48683e+001
21
6.3000000000e+003
6.74903e+001
22
8.0000000000e+003
6.70415e+001
23
1.0000000000e+004
6.67820e+001
24
1.2500000000e+004
6.49849e+001

测点4的记录数据
序号
频率（Hz）
声压级（dB）
1
6.3000000000e+001
2.41419e+001
2
8.0000000000e+001
2.85947e+001
3
1.0000000000e+002
4.05011e+001
4
1.2500000000e+002
3.30512e+001
5
1.6000000000e+002
3.69295e+001
6
2.0000000000e+002
4.30127e+001
7
2.5000000000e+002
4.66979e+001
8
3.1500000000e+002
5.76067e+001
9
4.0000000000e+002
5.59737e+001
10
5.0000000000e+002
6.05978e+001
11
6.3000000000e+002
6.31712e+001
12
8.0000000000e+002
6.71766e+001
13
1.0000000000e+003
7.04580e+001
14
1.2500000000e+003
7.16968e+001
15
1.6000000000e+003
6.91766e+001
16
2.0000000000e+003
7.38660e+001
17
2.5000000000e+003
7.05139e+001
18
3.1500000000e+003
7.12660e+001
19
4.0000000000e+003
7.52949e+001
20
5.0000000000e+003
6.99514e+001
21
6.3000000000e+003
6.90324e+001
22
8.0000000000e+003
6.77035e+001
23
1.0000000000e+004
6.56655e+001
24
1.2500000000e+004
6.44730e+001

测点5的记录数据
序号
频率（Hz）
声压级（dB）
1
6.3000000000e+001
2.45747e+001
2
8.0000000000e+001
2.62489e+001
3
1.0000000000e+002
3.17236e+001
4
1.2500000000e+002
3.83195e+001
5
1.6000000000e+002
4.47805e+001
6
2.0000000000e+002
4.71485e+001
7
2.5000000000e+002
4.87424e+001
8
3.1500000000e+002
5.98320e+001
9
4.0000000000e+002
5.77249e+001
10
5.0000000000e+002
6.00334e+001
11
6.3000000000e+002
6.22407e+001
12
8.0000000000e+002
6.54265e+001
13
1.0000000000e+003
6.85357e+001
14
1.2500000000e+003
6.80967e+001
15
1.6000000000e+003
6.94998e+001
16
2.0000000000e+003
6.59071e+001
17
2.5000000000e+003
7.19332e+001
18
3.1500000000e+003
7.28463e+001
19
4.0000000000e+003
7.15122e+001
20
5.0000000000e+003
7.04118e+001
21
6.3000000000e+003
6.61315e+001
22
8.0000000000e+003
6.50594e+001
23
1.0000000000e+004
6.70321e+001
24
1.2500000000e+004
6.18396e+001

测点6的记录数据
序号
频率（Hz）
声压级（dB）
1
6.3000000000e+001
2.80322e+001
2
8.0000000000e+001
3.08437e+001
3
1.0000000000e+002
3.63733e+001
4
1.2500000000e+002
3.58923e+001
5
1.6000000000e+002
4.20785e+001
6
2.0000000000e+002
4.03788e+001
7
2.5000000000e+002
4.42155e+001
8
3.1500000000e+002
4.93321e+001
9
4.0000000000e+002
5.31587e+001
10
5.0000000000e+002
5.65769e+001
11
6.3000000000e+002
5.98299e+001
12
8.0000000000e+002
6.58934e+001
13
1.0000000000e+003
7.10451e+001
14
1.2500000000e+003
7.03120e+001
15
1.6000000000e+003
6.86253e+001
16
2.0000000000e+003
7.08321e+001
17
2.5000000000e+003
6.92552e+001
18
3.1500000000e+003
6.84775e+001
19
4.0000000000e+003
7.39125e+001
20
5.0000000000e+003
7.00372e+001
21
6.3000000000e+003
6.67916e+001
22
8.0000000000e+003
6.54144e+001
23
1.0000000000e+004
6.61451e+001
24
1.2500000000e+004
6.39371e+001

测点7的记录数据
序号
频率（Hz）
声压级（dB）
1
6.3000000000e+001
5.87263e+001
2
8.0000000000e+001
5.72207e+001
3
1.0000000000e+002
5.17067e+001
4
1.2500000000e+002
4.85478e+001
5
1.6000000000e+002
4.67473e+001
6
2.0000000000e+002
4.57892e+001
7
2.5000000000e+002
4.72410e+001
8
3.1500000000e+002
5.55667e+001
9
4.0000000000e+002
5.69116e+001
10
5.0000000000e+002
5.87219e+001
11
6.3000000000e+002
6.28192e+001
12
8.0000000000e+002
6.96265e+001
13
1.0000000000e+003
7.27475e+001
14
1.2500000000e+003
7.01544e+001
15
1.6000000000e+003
6.93641e+001
16
2.0000000000e+003
7.13205e+001
17
2.5000000000e+003
7.50484e+001
18
3.1500000000e+003
7.33248e+001
19
4.0000000000e+003
7.40256e+001
20
5.0000000000e+003
6.90320e+001
21
6.3000000000e+003
6.61139e+001
22
8.0000000000e+003
6.72157e+001
23
1.0000000000e+004
6.51052e+001
24
1.2500000000e+004
6.15588e+001

测点8的记录数据
序号
频率（Hz）
声压级（dB）
1
6.3000000000e+001
2.79751e+001
2
8.0000000000e+001
2.91717e+001
3
1.0000000000e+002
3.74784e+001
4
1.2500000000e+002
3.70162e+001
5
1.6000000000e+002
4.25198e+001
6
2.0000000000e+002
4.26275e+001
7
2.5000000000e+002
4.58913e+001
8
3.1500000000e+002
5.66895e+001
9
4.0000000000e+002
5.57578e+001
10
5.0000000000e+002
5.86699e+001
11
6.3000000000e+002
6.35316e+001
12
8.0000000000e+002
7.03141e+001
13
1.0000000000e+003
7.40493e+001
14
1.2500000000e+003
6.95273e+001
15
1.6000000000e+003
6.67842e+001
16
2.0000000000e+003
7.21716e+001
17
2.5000000000e+003
7.64255e+001
18
3.1500000000e+003
7.49823e+001
19
4.0000000000e+003
7.39499e+001
20
5.0000000000e+003
7.01009e+001
21
6.3000000000e+003
7.08282e+001
22
8.0000000000e+003
6.72810e+001
23
1.0000000000e+004
6.49728e+001
24
1.2500000000e+004
6.54819e+001

测点9的记录数据
序号
频率（Hz）
声压级（dB）
1
6.3000000000e+001
2.66892e+001
2
8.0000000000e+001
2.83850e+001
3
1.0000000000e+002
3.63599e+001
4
1.2500000000e+002
3.64220e+001
5
1.6000000000e+002
4.21315e+001
6
2.0000000000e+002
4.34957e+001
7
2.5000000000e+002
4.57244e+001
8
3.1500000000e+002
4.96399e+001
9
4.0000000000e+002
5.32388e+001
10
5.0000000000e+002
5.77944e+001
11
6.3000000000e+002
6.40408e+001
12
8.0000000000e+002
6.64229e+001
13
1.0000000000e+003
7.01934e+001
14
1.2500000000e+003
6.94370e+001
15
1.6000000000e+003
6.63248e+001
16
2.0000000000e+003
7.21457e+001
17
2.5000000000e+003
7.47658e+001
18
3.1500000000e+003
7.42276e+001
19
4.0000000000e+003
7.61133e+001
20
5.0000000000e+003
7.03365e+001
21
6.3000000000e+003
6.65539e+001
22
8.0000000000e+003
6.75153e+001
23
1.0000000000e+004
6.48808e+001
24
1.2500000000e+004
6.45882e+001

测点10的记录数据
序号
频率（Hz）
声压级（dB）
1
6.3000000000e+001
2.79003e+001
2
8.0000000000e+001
2.71257e+001
3
1.0000000000e+002
3.56100e+001
4
1.2500000000e+002
3.31189e+001
5
1.6000000000e+002
3.83103e+001
6
2.0000000000e+002
4.24349e+001
7
2.5000000000e+002
4.67852e+001
8
3.1500000000e+002
5.70304e+001
9
4.0000000000e+002
5.96226e+001
10
5.0000000000e+002
6.35944e+001
11
6.3000000000e+002
6.63078e+001
12
8.0000000000e+002
6.95178e+001
13
1.0000000000e+003
6.95546e+001
14
1.2500000000e+003
6.91461e+001
15
1.6000000000e+003
6.87565e+001
16
2.0000000000e+003
7.12519e+001
17
2.5000000000e+003
7.27371e+001
18
3.1500000000e+003
6.92435e+001
19
4.0000000000e+003
7.12147e+001
20
5.0000000000e+003
6.92732e+001
21
6.3000000000e+003
6.57371e+001
22
8.0000000000e+003
6.60844e+001
23
1.0000000000e+004
6.33321e+001
24
1.2500000000e+004
6.19473e+001

测点11的记录数据
序号
频率（Hz）
声压级（dB）
1
6.3000000000e+001
5.98484e+001
2
8.0000000000e+001
5.85147e+001
3
1.0000000000e+002
5.84183e+001
4
1.2500000000e+002
5.78698e+001
5
1.6000000000e+002
5.81615e+001
6
2.0000000000e+002
5.90101e+001
7
2.5000000000e+002
5.96175e+001
8
3.1500000000e+002
6.28416e+001
9
4.0000000000e+002
6.25115e+001
10
5.0000000000e+002
6.21682e+001
11
6.3000000000e+002
6.85665e+001
12
8.0000000000e+002
7.22069e+001
13
1.0000000000e+003
7.08437e+001
14
1.2500000000e+003
7.12458e+001
15
1.6000000000e+003
7.19315e+001
16
2.0000000000e+003
6.81861e+001
17
2.5000000000e+003
6.89476e+001
18
3.1500000000e+003
6.91600e+001
19
4.0000000000e+003
7.85703e+001
20
5.0000000000e+003
7.22423e+001
21
6.3000000000e+003
7.12917e+001
22
8.0000000000e+003
6.69062e+001
23
1.0000000000e+004
6.57065e+001
24
1.2500000000e+004
6.40216e+001
测点12的记录数据
序号
频率（Hz）
声压级（dB）
1
6.3000000000e+001
4.15306e+001
2
8.0000000000e+001
3.72496e+001
3
1.0000000000e+002
3.76830e+001
4
1.2500000000e+002
4.05717e+001
5
1.6000000000e+002
4.56057e+001
6
2.0000000000e+002
4.91665e+001
7
2.5000000000e+002
4.93840e+001
8
3.1500000000e+002
5.89830e+001
9
4.0000000000e+002
6.10921e+001
10
5.0000000000e+002
6.30995e+001
11
6.3000000000e+002
6.40254e+001
12
8.0000000000e+002
6.06420e+001
13
1.0000000000e+003
6.56070e+001
14
1.2500000000e+003
6.38366e+001
15
1.6000000000e+003
6.54321e+001
16
2.0000000000e+003
6.51974e+001
17
2.5000000000e+003
7.21538e+001
18
3.1500000000e+003
7.75686e+001
19
4.0000000000e+003
7.67046e+001
20
5.0000000000e+003
7.06445e+001
21
6.3000000000e+003
6.63015e+001
22
8.0000000000e+003
6.67562e+001
23
1.0000000000e+004
6.37474e+001
24
1.2500000000e+004
6.33128e+001

测点13的记录数据
序号
频率（Hz）
声压级（dB）
1
6.3000000000e+001
2.60514e+001
2
8.0000000000e+001
3.12378e+001
3
1.0000000000e+002
4.26058e+001
4
1.2500000000e+002
3.62954e+001
5
1.6000000000e+002
3.85188e+001
6
2.0000000000e+002
4.20659e+001
7
2.5000000000e+002
4.51887e+001
8
3.1500000000e+002
5.79194e+001
9
4.0000000000e+002
5.92190e+001
10
5.0000000000e+002
6.05264e+001
11
6.3000000000e+002
6.37646e+001
12
8.0000000000e+002
6.74215e+001
13
1.0000000000e+003
7.10428e+001
14
1.2500000000e+003
7.28276e+001
15
1.6000000000e+003
7.10097e+001
16
2.0000000000e+003
7.41620e+001
17
2.5000000000e+003
7.13852e+001
18
3.1500000000e+003
7.12102e+001
19
4.0000000000e+003
7.50648e+001
20
5.0000000000e+003
7.21114e+001
21
6.3000000000e+003
6.59741e+001
22
8.0000000000e+003
6.77342e+001
23
1.0000000000e+004
6.21186e+001
24
1.2500000000e+004
6.42508e+001

测点14的记录数据
序号
频率（Hz）
声压级（dB）
1
6.3000000000e+001
2.76973e+001
2
8.0000000000e+001
3.00455e+001
3
1.0000000000e+002
4.06564e+001
4
1.2500000000e+002
3.70782e+001
5
1.6000000000e+002
4.20851e+001
6
2.0000000000e+002
4.41290e+001
7
2.5000000000e+002
4.64160e+001
8
3.1500000000e+002
5.55860e+001
9
4.0000000000e+002
5.65433e+001
10
5.0000000000e+002
5.87743e+001
11
6.3000000000e+002
6.08132e+001
12
8.0000000000e+002
6.59209e+001
13
1.0000000000e+003
6.98789e+001
14
1.2500000000e+003
7.14929e+001
15
1.6000000000e+003
7.17307e+001
16
2.0000000000e+003
7.08396e+001
17
2.5000000000e+003
6.86726e+001
18
3.1500000000e+003
7.18535e+001
19
4.0000000000e+003
8.28384e+001
20
5.0000000000e+003
7.81801e+001
21
6.3000000000e+003
6.69511e+001
22
8.0000000000e+003
6.81851e+001
23
1.0000000000e+004
6.60364e+001
24
1.2500000000e+004
6.34845e+001

测点15的记录数据
序号
频率（Hz）
声压级（dB）
1
6.3000000000e+001
3.04752e+001
2
8.0000000000e+001
3.06822e+001
3
1.0000000000e+002
3.71829e+001
4
1.2500000000e+002
3.85181e+001
5
1.6000000000e+002
4.43946e+001
6
2.0000000000e+002
4.68850e+001
7
2.5000000000e+002
4.75112e+001
8
3.1500000000e+002
4.94897e+001
9
4.0000000000e+002
5.28509e+001
10
5.0000000000e+002
5.82277e+001
11
6.3000000000e+002
6.35546e+001
12
8.0000000000e+002
6.40673e+001
13
1.0000000000e+003
6.76168e+001
14
1.2500000000e+003
6.96859e+001
15
1.6000000000e+003
6.91576e+001
16
2.0000000000e+003
7.21760e+001
17
2.5000000000e+003
7.28249e+001
18
3.1500000000e+003
7.20659e+001
19
4.0000000000e+003
7.65134e+001
20
5.0000000000e+003
6.95307e+001
21
6.3000000000e+003
6.66506e+001
22
8.0000000000e+003
6.78928e+001
23
1.0000000000e+004
6.45399e+001
24
1.2500000000e+004
6.48202e+001

测点16的记录数据
序号
频率（Hz）
声压级（dB）
1
6.3000000000e+001
2.96126e+001
2
8.0000000000e+001
2.85342e+001
3
1.0000000000e+002
3.90655e+001
4
1.2500000000e+002
3.67615e+001
5
1.6000000000e+002
3.88944e+001
6
2.0000000000e+002
4.10276e+001
7
2.5000000000e+00